Bimetallic catalyst for producing polyethylene resins with bimodal molecular weight distribution, its preparation and use

ABSTRACT

Bimetallic catalyst for producing polyethylene resins with a bimodal molecular weight distribution, its preparation and use. The catalyst is obtainable by a process which includes contacting a support material with an organomagnesium component and carbonyl-containing component. The support material so treated is contacted with a non-metallocene transition metal component to obtain a catalyst intermediate, the latter being contacted with an aluminoxane component and a metallocene component, This catalyst may be further activated with, e.g., alkylaluminum cocatalyst, and contacted, under polymerization conditions, with ethylene and optionally one or more comonomers, to produce ethylene homo- or copolymers with a bimodal molecular weight distribution and improved resin swell properties in a single reactor. These ethylene polymers are particularly suitable for blow molding applications.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 10/433,228, filed May 29, 2003, now issued as U.S. Pat. No. ______,and is herein incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a supported bimetallic catalyst, itspreparation and its use in the production of homo- and copolymers ofethylene (polyethylene resins) with a bimodal molecular weightdistribution (MWD) in a single reactor. The present invention alsorelates to polyethylene resins produced with a catalyst that includesthe supported bimetallic catalyst.

2. Background

Swell characteristics play an important role in determining theprocessability of high density polyethylene (HDPE) blow molding resins,such as those used for the manufacture of bottles and similar articles.More particularly, when a polymer is melted and then forced through asmall opening (orifice) the polymer may swell (expand) to a diameterlarger than the orifice. This phenomenon is commonly referred to as“polymer swell”. “Intrinsic swell” is the polymer swell as measured froma polymer sample directly after manufacture. To obtain the intrinsicswell of a polymer sample, the polymer sample must be completelystabilized with an additive package (i.e., compounds that prevent anypolymer degradation when the polymer is melted) during the time theswell measurement is being made.

It is known that HDPE blow molding resins are produced in the gas phaseand in a single reactor by means of traditional chromium-basedcatalysts. However, the intrinsic swell of the resulting resins often istoo high for commercial applications; i.e., so high that it contributesto, for example, unacceptably high bottle weight, poor bottle handle andfixtures formation, and excessive flash. One option for lowering theswell of such resins is to degrade them in the presence of air alongwith high stresses and temperature. However, after the swell has beenlowered due to polymer degradation, the resin needs to be stabilizedwith antioxidants to prevent further polymer degradation. Another optionfor lowering the swell is the use of peroxides having high decompositiontemperatures to produce controlled degradation. A potential disadvantageof this technique is that it requires well-controlled downstreamprocessing of the resin, which requires maintenance and adds to the costof the resin. Both of these controlled degradation techniques can leadto contamination of the resin and/or color and odor problems in theresin. Moreover, these polymer degradation processes slow down themanufacturing rates (polymer output/time unit) and may be difficult tocontrol. On the other hand, if the swell of a particular polymer is toolow for commercial applications, nothing can be done to increase swellto the necessary value.

Generally, high performance blow molding resins have a bimodal molecularweight distribution (MWD). As used herein, “resin having a bimodal MWD”means that the resin comprises at least two polymer components, one ofthe at least two components having a higher average molecular weight(hereinafter sometimes referred to as the “HMW polymer component”) thananother of the at least two components (hereinafter sometimes referredto as the “LMW polymer component”). Resins with a bimodal MWD can beproduced in a single reactor using the technology disclosed in, forexample, U.S. Pat. No. 5,539,076, discussed below, or by the use of aseries of reactors or reaction steps. For example, bimodal MWDpolyethylene resins can be produced in tandem slurry processes, butoften suffer from low intrinsic swell. Low intrinsic swell leads toproblems with webbing in the bottle, poor formation of handles andbottle fixtures, and bottle extrusion problems.

U.S. Pat. No. 5,032,562 to Lo et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, discloses asupported olefin polymerization catalyst composition comprising aprecursor and a catalyst activator. The catalyst is used in the presenceof small amounts of hydrogen to produce polyolefins having a multimodalMWD in a single reactor. The catalyst comprises a dialkylmagnesiumcomponent, a zirconocene and a non-metallocene titanium and/or vanadiumcompound. It is mentioned that the precursor may optionally also includean organic compound, suitable examples thereof being alcohols, ketones,esters, acids or organic silicates. Alcohols, such as 1-butanol, arestated to be the preferred organic compounds.

U.S. Pat. No. 5,539,076 to Nowlin et al., the disclosure of which is 10expressly incorporated herein by reference in its entirety, disclosesresins which are in situ catalytically produced polyethylene resinblends of a broad bimodal MWD that can be processed into films onexisting equipment and exhibit good processability in blown filmproduction and reduced tendency towards die-lip buildup and smoking inon-line operations. The preferred catalyst for producing these resinscomprises a catalyst including a support treated with a dialkylmagnesiumcompound, an aluminoxane, at least one metallocene and a non-metallocenetransition metal source as well as an alkylaluminum compound, e.g.,trimethylaluminum (TMA), as cocatalyst.

U.S. Pat. No. 5,614,456 to Mink et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, is directedto an activated catalyst composition for producing bimodal MWD highdensity and linear low density polyethylene resins, which activatedcatalyst does not require an alkylaluminum cocatalyst. A preferredcatalyst comprises, as support. silica impregnated with adialkylmagnesium compound and an organic alcohol reagent, e.g, butanol,The support is contacted with at least two transition metal compounds,at least one of which is a metallocene, e.g., zirconocene, and, asactivator, aluminoxane, either alone or admixed with the metallocenecompound.

U.S. Pat. No. 5,260,245 to Mink et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, describes acatalyst for producing higher flow index linear low density polyethylenewith relatively narrower molecular weight distributions. The catalyst isformed by treating silica having reactive OH groups with adialkylmagnesium compound and a carbonyl-containing compound to form anintermediate which is subsequently treated with a transition metalcompound to form a catalyst precursor. The catalyst precursor isactivated with triethylaluminum.

SUMMARY

One embodiment of the present invention involves supported bimetalliccatalysts which can be used for the production of polyethylene resins ofbimodal MWD in a single reactor, which resins are especially suitablefor blow molding applications. The catalysts can be used to controlresin swell (in the following the terms “polymer swell” and “resinswell” will be used interchangeably) over a wide and commerciallysignificant range and are able to produce resins with the desired swellcharacteristics. Also, the catalysts can be used without the need foradditional is processing-induced resin modification; i.e, resin swelldoes not have to be lowered to a commercially acceptable level.

Another embodiment of the present invention is directed to thepolyethylene resins produced with corresponding catalysts. These resinscan be used to advantage in a wide range of applications, for example,blow molding, large part blow molding, pipe and pressure pipeapplications.

In one aspect the present invention relates to a process for making asupported bimetallic catalyst that is suitable for use in the productionof homopolymers and copolymers of ethylene with a bimodal molecularweight distribution in a single reactor. The process comprisescontacting a support material with an organomagnesium component and atleast one carbonyl-containing component selected from aldehydes andketones, whereafter the support material is contacted with anon-metallocene transition metal component to obtain a catalystintermediate. This intermediate is contacted with at least onealuminoxane and at least one metallocene component to prepare the finalbimetallic catalyst.

In one embodiment, the support material is a solid, particulatematerial. The solid particulate material may be silica.

In another embodiment, the organomagnesium component comprises acompound of the general formula (I):R¹ _(m)MgR² _(n)   (I)wherein R¹ and R² are the same or different alkyl groups each containingabout 2 to about 12 carbon atoms, preferably about 4 to about 8 carbonatoms, and m and n are each 0, 1 or 2, provided that the sum (m+n) isequal to the valence of Mg, a specific example of such adialkylmagnesium component being dibutylmagnesium.

According to another embodiment, the carbonyl-containing componentcomprises at least one compound of the general formula (II):R³—CO—R⁴   (II)wherein R³ and R⁴ are independently selected from optionally substitutedaliphatic groups, e.g., aliphatic groups containing 1 to about 20 carbonatoms, optionally substituted cycloaliphatic groups. e.g, cycloaliphaticgroups containing about 5 to about 8 carbon atoms, and optionallysubstituted aromatic groups, e.g., aromatic groups containing about 6 toabout 20 carbon atoms, and R⁴ can additionally be hydrogen. Specificexamples of such carbonyl-containing components include benzaldehyde,p-tolualdehyde, salicylaldehyde, butylaldehyde, 2-pentanone and3′-methylacetophenone.

In a further embodiment, the non-metallocene transition metal componentcomprises at least one compound that contains a Group IV or V transitionmetal, e.g., titanium and/or vanadium. The non-metallocene transitionmetal component may also include halogen. The non-metallocene transitionmetal component may be a tetravalent titanium compound, e.g., titaniumtetrachloride.

According to still another embodiment, the metallocene compoundcomprises at least one compound of the general formula (III):Cp_(x)MA_(Y)   (III)wherein x is at least 1, M is titanium, zirconium or hafnium; Cprepresents optionally substituted cyclopentadienyl, e.g., unsubstitutedcyclopentadienyl or cyclopentadienyl substituted by an alkyl groupcontaining I to about 8 carbon atoms (such as n-butylcyclopentadieny);optionally substituted cyclopentadienyl that is part of a bicyclic ortricyclic moiety; or, when x is 2, the cyclopentadienyl moieties may belinked by a bridging group. A is selected from halogen atom, hydrogenatom, alkyl group and combinations thereof, and the sum (x+y) is equalto the valence of M. For example, M may represent Zr, A may representhalogen and x may equal 2. Specific examples of metallocene componentsof the above general formula are bis(cyclopentadienyl)zirconiumdichloride and bis(n-butylcyclopentadienyl) zirconium dichloride.

In yet another embodiment, the aluminoxane is selected frommethylaluminoxane (MAO), modified methylaluminoxanes (MMAO) and mixturesthereof, and may particularly be MAO.

Regarding the relative proportions of the various reagents for makingthe bimetallic catalyst, according to one embodiment, the molar ratio ofdialkylmagnesium component to carbonyl-containing component is fromabout 1:5 to about 15:1. In another embodiment, the atomic ratio of Mgin the dialkylmagnesium component to transition metal in thenon-metallocene transition metal component is in the range from about0.5:1 to about 5:1. In still another embodiment, the atomic ratio oftransition metal in the non-metallocene transition metal component tometal in the metallocene component ranges from about 1:1 to about 30:1.According to a further embodiment, the atomic ratio of metal in themetallocene component to Al in the aluminoxane ranges from about 1:10 toabout 1:1000.

Another aspect of the present invention is a process for making asupported bimetallic catalyst suitable for use in the production ofhomopolymers and copolymers of ethylene with a bimodal molecular weightdistribution in a single reactor, which process comprises providing aslurry of silica calcined at a temperature from about 200° C. to about850° C. in a non-polar liquid medium (in the following, the terms“non-polar liquid medium” and “non-polar solvent” will be usedinterchangeably) and adding to the slurry a dialkylmagnesium componentwhose alkyl groups each contain about 4 to about 8 carbon atoms. To theresulting slurry there is added at least one carbonyl-containingcomponent selected from benzaldehyde, p-tolualdehyde, salicylaldehyde,butylaldehyde, 2-pentanone and 3′-methyl acetophenone, the amount ofadded carbonyl-containing component being such as to afford a molarratio of dialkylmagnesium component to carbonyl-containing component ofabout 1:1 to about 2:1. Subsequent addition of titanium tetrachlorideresults in the formation of a slurry of a catalyst intermediate in anon-polar solvent, from which the liquid phase is removed to obtain asubstantially dry, free-flowing intermediate catalyst. A slurry of thiscatalyst intermediate in a non-polar solvent is prepared. Next, asolution formed by contacting a zirconocene compound withmethylaluminoxane in an aromatic solvent is added to theintermediate-containing slurry, which results in the formation of aslurry of a bimetallic catalyst. The bimetallic catalyst is recoveredfrom the slurry by separating the liquid phase from the catalyst.

Another aspect of the present invention is formed by the supportedbimetallic catalyst that is obtainable by the above process. In oneembodiment, the catalyst comprises a solid support which includes atleast one non-metallocene transition metal source, at least onemetallocene component, and at least one aluminoxane, the support treatedwith an organomagnesium component and at least one carbonyl-containingcomponent selected from aldehydes and ketones.

The present invention also relates to a catalyst composition includingthe above-described catalyst and a cocatalyst. In one embodiment, thecocatalyst comprises at least one compound of the general formula (IV):R⁵ _(a)AlX_(b)   (IV)wherein a is 1, 2 or 3, R⁵ is an alkyl group containing 1 to about 10carbon atoms, X represents hydrogen or halogen and b is 0, 1 or 2,provided that the sum (a+b) is 3.

Another aspect of the present invention is a process for producing ahomopolymer or copolymer of ethylene having a bimodal MWD and producedin a single reactor with a bimetallic catalyst as described above, aswell as the ethylene polymers produced thereby. The process comprisescontacting ethylene and optionally one or more comonomers underpolymerization conditions, e.g., in the gas phase, with the bimetalliccatalyst. The copolymer of ethylene may be a copolymer of ethylene andat least one α-olefin having about 3 to about 10 carbon atoms such as,e.g., 1-hexene.

The ethylene polymers of the present invention may have an annular dieswell at a shear rate of 210 s⁻¹ of about 0.3 g to about 0.5 g and anannular die swell at a shear rate of 6300 s⁻¹ of about 0.55 g to about0.95 g. They may also have a density in the range of about 0.915 toabout 0.970 g/cm³ and may particularly be high density polyethylenes. Inanother embodiment, the ethylene polymers may have a flow index (FI) inthe range of about 1 g/10 mm to about 100 g/10 mm. Also, they maycomprise deactivated catalyst.

The present invention also relates to a blow molded article producedfrom the ethylene polymers of the present invention such as, e.g. abottle.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed descriptionwhich follows, in reference to the drawings by way of non-limitingexamples of exemplary embodiments of the present invention. In thedrawings:

FIG. 1 shows a GPC curve of the resins produced in PolymerizationExamples 6 and 7; and

FIG. 2 shows a GPC curve of the resins produced in PolymerizationExamples 7 and 10.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present inventiononly, and are presented to provide what is believed to be the mostuseful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show structural details of the present invention in moredetail than is necessary for the fundamental understanding of thepresent invention, the description making apparent to those skilled inthe art how the several forms of the present invention may be embodiedin practice.

All percent measurements in this application, unless otherwise stated,are measured by weight based upon 100% of a given sample weight. Thus,for example, 30% represents 30 weight parts out of every 100 weightparts of the sample.

Unless otherwise stated, a reference to a compound or component includesthe compound or component by itself, as well as in combination withother compounds or components, such as mixtures of compounds (e.g.,mixtures of isomers).

Further, when an amount, concentration, or other value or parameter, isgiven as a list of upper preferable values and lower preferable values,this is to be understood as specifically disclosing all ranges formedfrom any pair of an upper preferred value and a lower preferred value,regardless whether ranges are separately disclosed.

A preferred synthesis of the supported bimetallic catalyst of thepresent invention comprises two stages: synthesis of the supportedcatalyst intermediate (preferably in the given order of consecutivesteps and without isolation of a dry product until after theincorporation of the non-metallocene transition metal compound); andsynthesis of the final supported catalyst. Thus the synthesis ispreferably carried out in a series of several consecutive steps underinert conditions in the substantial absence of water and molecularoxygen.

According to this preferred synthesis, support material is firstslurried in a non-polar solvent. Support materials for preparing thebimetallic catalysts of the present invention comprise solid,particulate, porous materials and may include support materialsdisclosed in U.S. Pat. No. 4,173,547, the disclosure of which isexpressly incorporated herein by reference in its entirety. Such supportmaterials include, but are not limited to, metal oxides, hydroxides,halides or other metal salts, such as sulfates, carbonates, phosphates,silicates, and combinations thereof, and may be amorphous orcrystalline. Some preferred support materials include silica, aluminaand combinations thereof Support material particles may have any shape,and are preferably approximately spherical (such as are obtainable, forexample, by spray-drying).

Preferred support materials comprise particles, the optimum size ofwhich can easily be established by one of ordinary skill in the art. Asupport material that is too coarse may lead to unfavorable results,such as low bulk density of the resulting polymer powder. Thus,preferred support materials comprise particles with average size, e.g.,diameter, smaller than about 250 μm, more preferably smaller than about200 μm, most preferably smaller than about 80 μm. Preferred supportmaterials comprise particles larger than about 0.1 μm, more preferablylarger than about 10 μm in size, because smaller silica particles mayproduce small polymer particles (fines) which may cause reactorinstability.

Support material is preferably porous, as porosity increases the surfacearea of the support material, which, in turn, provides more sites forreaction. The specific surface areas may be measured in accordance withBritish Standards BS 4359, volume 1 (1969). The specific surface area ofsupport material used in accordance with the present invention ispreferably at least about 3 m²/g, more preferably at least about 50m²/g, and most preferably at least about 150 m²/g, e.g., about 300 m²/g.There is no preferred upper limit to support material specific surfacearea. Without limiting the present invention, the specific surface areaof support material is generally less than about 1500 m²/g.

The internal porosity of support material may be measured as the ratiobetween the pore volume and the weight of the material and can bedetermined by the BET technique, such as described by Brunauer et al.,J. Am. Chem. Soc., 60, pp. 209-319 (1938). The internal porosity ofsupport material is preferably larger than about 0.2 cm³/g, morepreferably larger than about 0.6 cm³/g. There is no preferred upperlimit to support material internal porosity, which, as a practicalmatter, is limited by particle size and internal pore diameter. Thus,without limiting the present invention, internal porosity is generallyless than about 2.0 cm3/g.

Preferred support materials for use in the present invention comprisesilica, particularly amorphous silica, and most preferably high surfacearea amorphous silica. Such support materials are commercially availablefrom a number of sources, and include a material marketed under thetradenames of Davison 952 or Davison 955 by the Davison ChemicalDivision of W.R. Grace and Company, or Crosfield ES70 by CrosfieldLimited (surface area=300 m²/g; pore volume 1.65 cm³/g). The silica isin the form of spherical particles, which are obtained by a spray-dryingprocess. As procured, these silicas are not calcined (dehydrated).

Because organometallic components used in the preparation of thecatalysts and catalyst compositions of the present invention may reactwith water, the support material should preferably be substantially dry.Water that is physically bound to the support material, therefore, ispreferably removed, such as by calcination, prior to forming abimetallic catalyst according to the present invention.

Preferred calcined support materials comprise support material that hasbeen calcined at a temperature higher than about 100° C., morepreferably higher than about 150° C., even more preferably higher thanabout 200° C., e.g., higher than about 250° C. As sintering of thesupport material is preferably avoided, calcination is preferablyeffected at a temperature that is below the sintering temperature of thesupport material. Calcination of a support material, e.g., silica, isconveniently carried out at a temperature of not higher than about 850°C., e.g., not higher than about 650° C. Exemplary calcinationtemperatures are about 300° C., about 600° C., and about 800° C. Totalcalcination times usually are not shorter than about 4 hours, preferablynot shorter than about 6 hours, whereas calcination times longer than 24hours, or even longer than 12 hours offer no particular advantage.

Calcination of support material can be performed using any procedureknown to those of ordinary skill in the art, and the present inventionis not limited by the calcination method. A preferred method ofcalcination is disclosed by T. E. Nowlin et al., “Ziegler-NattaCatalysts on Silica for Ethylene Polymerization,” J. Polym. Sci., PartA: Polymer Chemistry, vol. 29, 1167-1173 (1991), the disclosure of whichis expressly incorporated herein by reference in its entirety.

As used in this disclosure, support material as used in the Examplesbelow may, for example, be prepared as follows. In a fluidized-bed,silica (e.g., Davison 955), is heated in steps from ambient temperatureto the desired calcining temperature (e.g., 600° C.). The silica ismaintained at about this temperature for about 4 to about 16 hours,after which it is allowed to cool to ambient temperature. Thecalcination temperature primarily affects the number of OH groups on thesupport surface; i.e., the number of OH groups on the support surface(silanol groups in the case of silica) is approximately inverselyproportional to the temperature of drying or dehydration: the higher thetemperature the lower the hydroxyl group content. In other words, ateach calcination temperature the support (e.g., silica) reaches acertain OH concentration, after which additional heating has no furthereffect on the OH concentration.

The slurry of the support material in the non-polar solvent is preparedby introducing the support material into the solvent, preferably whilestirring, and heating the mixture to about 25 to about 70° C.,preferably to about 40 to about 60° C. The most suitable non-polarsolvents are materials which are liquid at reaction temperatures and inwhich all of the reactants used later during the catalyst preparation,i.e., organomagnesium components, carbonyl-containing components andtransition metal components, are at least partially soluble. Preferrednon-polar solvents are alkanes, particularly those containing about 5 toabout 10 carbon atoms, such as isopentane, hexane, isohexane, n-heptane,isoheptane, octane, nonane, and decane. However, other materials,including cycloalkanes, particularly those containing about 5 to about10 carbon atoms, such as cyclohexane and methylcyclohexane, and aromaticsolvents, particularly those containing about 6 to about 12 carbonatoms, such as benzene, toluene, ethylbenzene and the xylenes, may alsobe used. Of course, it is also possible to use solvent mixtures. Thepreferred non-polar solvents are isopentane and isohexane, withisopentane being particularly preferred (due to its low boiling pointwhich makes its removal convenient and fast).

Prior to use, the non-polar solvent should be purified, such as bypercolation through silica gel and/or molecular sieves, to remove tracesof water, molecular oxygen, polar compounds, and other materials capableof adversely affecting catalyst activity. It is to be noted that thetemperature of the slurry before addition of the non-metallocenetransition metal component should not be in excess of 90° C., sinceotherwise a deactivation of the transition metal component is likely toresult. Accordingly, all catalyst synthesis steps are preferably carriedout at a temperature below 90° C., even more preferable below 80° C.

Following the preparation of a slurry of the support material in anon-polar solvent, the slurry is contacted with an organomagnesiumcomponent.

Preferred organomagnesium components for use in the present inventioninclude dialkylmagnesium components of the general formula (I):R¹ _(m)MgR² _(n)   (I)wherein R¹ and R² are the same or different branched or unbranched alkylgroups containing about 2 to about 12 carbon atoms, preferably about 4to about 10 carbon atoms, and even more preferably about 4 to about 8carbon atoms, and m and n are each 0, 1 or 2, provided that the sum(m+n) is equal to the valence of Mg. The most preferred dialkylmagnesiumcomponent for use in the present invention is dibutylmagnesium. Ofcourse, it is also possible to use more than one organomagnesiumcomponent, e.g., two different organomagnesium components.

The purpose of the organomagnesium component is to increase the activityof the catalyst. For a better understanding of the role of theorganomagnesium component for the performance of polymerizationcatalysts such as those disclosed herein, reference may be made to theabove-mentioned article by T. E. Nowlin et al. in J. Polym. Sci.: PartA: Polymer Chemistry, Vol. 29, 1167-1173 (1991). The amount oforganomagnesium component will generally be greater than about 0.3mmol/g, more preferably greater than about 0.5 mmol/g, even morepreferably greater than 0.7 mmol/g, where the amount of organomagnesiumcomponent is given as mmol Mg/g of support material. In the synthesis ofthe catalyst of the present invention, it is desirable to add not moreorganomagnesium component than will be deposited—physically orchemically—into the support, since any excess of the organomagnesiumcomponent in the liquid phase may react with other chemicals used forthe catalyst synthesis and cause precipitation outside of the support.The drying temperature of the support materials affects the number ofsites on the support available for the dialkylmagnesium component: thehigher the drying temperature the lower the number of sites. Thus, theexact ratio of organomagnesium component to support will vary and shouldbe determined on a case-by-case basis to assure that preferably only somuch of the organomagnesium component is added to the slurry as will bedeposited into the support without leaving excess organomagnesiumcomponent in the liquid phase. Thus the ratios given below are intendedonly as an approximate guideline, and the exact amount oforganomagnesium component is to be controlled by the functionallimitation discussed above; i.e., it should preferably not be greaterthan that which can completely be deposited into the support. Theappropriate amount of the organomagnesium component can be determined inany conventional manner, e.g, by adding the organomagnesium component tothe slurry of the support material until free organomagnesium componentis detected in the liquid phase (e.g., by taking a sample of the liquidphase and analyzing it for Mg by one of several analytical proceduresknown to one of ordinary skill in the art). If organomagnesium componentis added in excess of the amount deposited into the support material, itcan be removed, e.g., by filtration and washing of the support material.However, this is less desirable than the embodiment described above.

For example, for the silica support heated at about 600° C., the amountof the organomagnesium component added to the slurry will generally beless than about 1.7 mmol/g, preferably less than about 1.4 mmol/g, evenmore preferably less than about 1.1 mmol/g.

The treatment of the support material with the organomagnesium componentcan in principle be carried out at any temperature at which theorganomagnesium component is stable. The contacting of the slurry of thesupport material in a non-polar solvent with the organomagnesiumcomponent will generally be carried out at a temperature between roomtemperature (e.g., 20° C.) and 80° C. Preferably, the addition iscarried out at slightly elevated temperature, e.g., at a temperature ofat least about 30° C., even more preferably at least about 40° C. Afterthe addition of the organomagnesium component is complete, the slurrywill usually be stirred, preferably at about the temperature ofaddition, for a sufficient time to allow the organomagnesium componentto react and/or interact with the support material substantiallycompletely. Generally, this time will be not less than about 0.1 hours,preferably not less than about 0.5 hours, although stirring for morethan about 2.0 hours will not bring about any significant furtherreaction/interaction.

Next, the support treated with the organomagnesium component iscontacted with a carbonyl-containing component, i.e., an aldehyde and/orketone. The carbonyl-containing component is used to modify thenon-metallocene transition metal component of the bimetallic catalyst ofthe present invention. Because the non-metallocene transition metalcatalyst component produces the HMW polymer component of thepolyethylene resin with a bimodal MWD, the carbonyl-containing componenthas a direct effect on the polymer properties of the HMW polymercomponent. Different carbonyl-containing components afford differentresults (to a certain extent) with regard to the weight fraction, theaverage molecular weight and the MWD of the HMW polymer component. Theseresults can readily be established by one of ordinary skill in the art.

Preferred aldehydes/ketones for use in the present invention are thoseof the general formula (II):R³—CO—R⁴   (II)wherein R³ and R⁴ are independently selected from optionallysubstituted, branched or unbranched, saturated or unsaturated (andpreferably saturated) aliphatic groups, optionally substitutedcycloaliphatic groups (saturated or unsaturated) and optionallysubstituted aromatic groups, and R⁴ can additionally be hydrogen.

The aliphatic groups will usually contain 1 to about 20 carbon atoms,more often 1 to about 10 carbon atoms and particularly 1 to about 6carbon atoms. Non-limiting examples thereof are methyl, ethyl, vinyl,propyl, isopropyl, allyl, n-butyl, isobutyl. pentyl and hexyl. Theoptional substituents of said aliphatic groups can be any radicals whichdo not adversely affect the performance of the catalyst.

The above cycloaliphatic groups generally contain about 5 to about 8carbon atoms, particularly about 5 to about 7 carbon atoms, notincluding the carbon atoms of one or more aliphatic groups (usuallyhaving 1 to 4 carbon atoms) that may be linked thereto. Non-limitingexamples of cycloaliphatic groups R³ and R⁴ are cyclopentyl, cyclohexyl,cyclooctyl, methylcyclopentyl and methylcyclohexyl.

The above aromatic groups usually will have about 6 to about 20 carbonatoms, particularly about 6 to about 12 carbon atoms. As used herein andin the appended claims, the term “aromatic groups” is meant to alsoinclude heteroaromatic groups in which one or more carbon atoms of thearomatic ring system are replaced by a heteroatom, particularly N, Oand/or S. Non-limiting examples of aromatic groups R³ and R⁴ suitablefor use in the present invention include phenyl, benzyl, tolyl, xylyl,ethylbenzyl, hydroxyphenyl, chlorophenyl, dichlorophenyl, naphthyl,methylnaphthyl, furyl, pyrrolyl, pyridinyl and thienyl, although thepresent invention is not limited to these examples.

Non-limiting examples of specific components of general formula (II)above are benzaldehyde, (o-, m- and p-)tolualdehyde,dimethylbenzaldehydes, trimethyl-benzaldehydes,tetramethylbenzaldehydes, pentamethylbenzaldehyde, ethylbenzaldehydes,triethylbenzaldehydes, triisopropylbenzaldehydes, salicylaldehyde,anisaldehyde, furfural, pyrrolaldehydes, acetaldehyde, propionaldehyde,butyraldehyde, valeraldehyde. isovaleraldehyde, acetone, butanone,2-pentanone, 3-pentanone, 2,6-dimethyl-4-pentanone, acetophenone,methylacetophenone, and benzophenone. Ethylenically unsaturatedcarbonyl-containing components (such as mesityl oxide, acrolein and thelike) may also be employed for the purposes of the present invention. Itis also possible to use more than one carbonyl-containing component,e.g., two aldehydes, one aldehyde and one ketone, or two ketones.Usually only one single carbonyl-containing component (or an isomericmixture thereof) will be employed. Benzaldehyde and tolualdehyde (boththe individual isomers and isomer mixtures) are particularly preferredcarbonyl-containing components for use in the preparation of thebimetallic catalyst of the present invention.

The amount of carbonyl-containing component employed is preferably suchthat it will react substantially completely with theorganomagnesium/support intermediate material formed after the additionof the organomagnesium component to the slurried support material.Generally the molar ratio of organomagnesium component (e.g.,dialkylmagnesium component) to carbonyl-containing component will be atleast about 1:5, more preferably at least about 1:2, and most preferredat least about 1:1. On the other hand it is preferred that said ratio isnot higher than about 15:1, particularly not higher than about 10:1 ,with a ratio of not higher than about 6:1, e.g., not higher than 2:1,being particularly preferred. Without wishing to be bound by any theory,it is assumed that one molecule of Mg species reacts/interacts with onemolecule of carbonyl-containing component.

Regarding the temperature at which the carbonyl-containing component isadded to the slurry of support material treated with the organomagnesiumcomponent, there are no particular restrictions besides the thermalstability of the materials involved. Generally, the addition will becarried out at a temperature between room temperature and the boilingpoint of the non-polar solvent of the slurry. As a matter of conveniencethe temperature will preferably be about the same as that at which theorganomagnesium component was added and at which the slurry oforganomagnesium component-treated support material was stirred beforethe addition of the carbonyl-containing component, respectively.Following the addition of the carbonyl-containing component, the slurrywill generally be stirred, preferably at about the temperature ofaddition, for a time period that is sufficient to allow thecarbonyl-containing component to substantially completely react/interactwith the organomagnesium component-treated support material. Thestirring time is generally at least about 0.5 hours, preferably at leastabout 1.0 hour, although stirring for more than about 2.0 hours usuallydoes not bring about any significant further reaction/interaction.

After the reaction/interaction with the carbonyl-containing component,the resulting slurry of support material is contacted with one or more(preferably one) non-metallocene transition metal component. During thisstep, the slurry temperature is preferably maintained at about 25 toabout 70° C., particularly at about 40 to about 60° C. As noted above,temperatures in the slurry of about 90° C. or greater are likely toresult in deactivation of the non-metallocene transition metal source.Suitable transition metal components used herein include those ofelements of Groups IV and V of the Periodic Table, particularlytitanium-containing and vanadium-containing compounds, provided thatthese compounds are at least somewhat soluble in non-polar solvents.Non-limiting examples of such compounds are titanium and vanadiumhalides, e.g., titanium tetrachloride, vanadium tetrachloride, vanadiumoxytrichloride, titanium and vanadium alkoxides, wherein the alkoxidemoiety has a branched or unbranched alkyl radical of 1 to about 20carbon atoms, preferably 1 to about 10 carbon atoms, and even morepreferably 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy andisopropoxy). The preferred transition metal components aretitanium-containing compounds, particularly tetravalenttitanium-containing compounds. The most preferred titanium compound isTiCl₄.

The amount of non-metallocene transition metal component(s) employed isat least in part determined by the desired ratio of HMW polymercomponent to LMW polymer component in the polyethylene resin with abimodal molecular weight distribution to be produced with the bimetalliccatalyst according to the present invention. In other words, because thenon-metallocene transition metal catalyst component will produce the HMWpolymer component and the metallocene catalyst component will producethe LMW polymer component, under otherwise identical polymerizationconditions the ratio of HMW polymer component to LMW polymer componentin the resulting polyethylene resin will increase with increasing molarratio of non-metallocene transition metal component(s) to metallocenecomponent(s) employed for the preparation of the supported bimetalliccatalyst. The total amount of catalyst components, on the other hand, islimited by the capability of the specific support material employed toaccommodate the catalyst components. Generally, however, thenon-metallocene transition metal is employed in an amount that resultsin an atomic ratio of Mg of the organomagnesium component (e.g.,dialkylmagnesium component employed to treat the support) to transitionmetal(s) in the non-metallocene transition metal component(s) of atleast about 0.5:1, more preferably at least about 1:1, and mostpreferred at least about 1.7:1. On the other hand it is preferred thatsaid ratio is not higher than about 5:1, particularly not higher thanabout 3:1, with a ratio of not higher than about 2:1 being particularlypreferred.

As already mentioned above, mixtures of non-metallocene transition metalcomponents may also he used and generally, no restrictions are imposedon the non-metallocene transition metal components which may beincluded. Any non-metallocene transition metal component that may beused alone may also be used in conjunction with other non-metallocenetransition metal components.

After the addition of the non-metallocene transition metal component(s)is complete, in one embodiment of the catalyst synthesis, the slurrysolvent is removed, e.g., by evaporation and/or filtration, to obtain apreferably free-flowing powder of a catalyst intermediate.

Next, incorporation of the metallocene component can be undertaken. Themetallocene component is activated with an aluminoxane.

Preferred metallocene components for use in the present invention havethe general formula (III):CPXMAY   (III)wherein x is at least 1, M is titanium, zirconium or hafnium, and Cprepresents unsubstituted, mono- or polysubstituted cyclopentadienyl,unsubstituted, mono- or polysubstituted cyclopentadienyl that is part ofa bicyclic or tricyclic moiety or, when x is 2, the cyciopentadienylmoieties may be linked by a bridging group. A represents halogen atom,hydrogen atom, alkyl group or combinations thereof, and the sum (x+y) isequal to the valence of M.

In the above formula of the metallocene component, the preferredtransition metal atom M is zirconium. The substituents on thecyclopentadienyl group, if present, will usually be (preferablystraight-chain) alkyl groups having 1 to about 6 carbon atoms, such as,e.g., methyl, ethyl, propyl, n-butyl, n-pentyl and n-hexyl. Thecyclopentadienyl group can also be part of an (optionally substituted)bicyclic or tricyclic moiety such as indenyl. tetrahydroindenyl,fluorenyl or a partially hydrogenated fluorenyl group. When the value ofx in the above general formula is equal to 2, the cyclopentadienylgroups can also be bridged, for example, by polymethylene ordialkylsilyl groups, such as —CH₂—, —CH, —CH₂—, —CR′R″— and —CR′R″—CRR″—where R′ and R″ are lower (e.g., C₁-C₄) alkyl groups or hydrogen atoms,—Si(CH₃)₂—, —Si(CH₃)₂—CH₂—CH₂—Si(CH₃)₂— and similar bridge groups. If Ain the above formula represents halogen it represents F, Cl, Br and/or Iand is preferably chlorine. If A represents an alkyl group, the alkylgroup preferably is a straight-chain or branched alkyl group containing1 to about 8 carbon atoms, such as methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, n-pentyl, n-hexyl and n-octyl. Of course, if in theabove general formula x is equal to or greater than 2 the groups Cp maybe the same or different. The same applies if y is equal to or greaterthan 2 with respect to the groups A which may also be the same ordifferent in that case.

Particularly suitable metallocene components for use in the preparationof the bimetallic catalyst of the present invention includebis(cyclopentadienyl)metal dihalides, bis(cyclopentadienyl)metalhydridohalides, bis(cyc1opentadienyl)metal monoalkyl monohalides,bis(cyclopentadienyl)metal dialkyls and bis(indenyl)metal dihalideswherein the metal is preferably zirconium or hafnium, the halide groupsare preferably chlorine and the alkyl groups (including cycloalkylgroups) preferably have 1 to about 6 carbon atoms. Illustrative,non-limiting examples of corresponding metallocenes include:

-   bis(indenyl)zirconium dichloride;-   bis(indenyl)zirconium dibromide;-   bis(indenyl)zirconium bis(p-toluenesulfonate);-   bis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;-   bis(fluorenyl)zirconium dichloride;-   ethylenebis(indenyl)zirconium dichloride;-   ethylenebis(indenyl)zirconium dibromide;-   ethylenebis(indenyl)dimethylzirconium;-   ethylenebis(indenyl)diphenylzirconium;-   ethylenebis(indenyl)methylzirconium chloride;-   ethylenebis(indenyl)zirconium bis(methanesulfonate);-   ethylenebis(indenyl)zirconium bis(p-toluenesulfonate);-   ethylenebis(indenyl)zirconium bis(trifluoromethansulfonate);-   ethylenebis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;-   isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride;-   isopropylidene(cyclopentadienyl)(methylcyclopentadieynl)zirconium    dichioride;-   dimethylsilylbis(cyclopentadienyl)zirconium dichloride;-   dimethylsilylbis(dimethylcyclopentadienyl)zirconium dichloride;-   dimethylsilylbis(trimethyl cyclopentadienyl)zirconium dichloride;-   dimethylsilylbis(indenyl)zirconium dichloride;-   dimethylsilylbis(indeny)zirconium bis(trifluoromethanesulfonate);-   dimethylsilylbis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;-   dimethylsilyl(cyclopentadienyl)(fluorenyl)zirconium dichloride;-   diphenylsilylbis(indenyl)zirconium dichloride;-   methylphenylsilylbis(indenyl)zirconium dichloride;-   bis(cyclopentadienyl)zirconium dichloride;-   bis(cyclopentadienyl)zirconium dibromide;-   bis(cyclopentadieny)methylzirconium chloride;-   bis(cyclopentadienyl)ethylzirconium chloride;-   bis(cyclopentadienyl)cyclohexylzirconium chloride;-   bis(cyclopentadienyl)phenylzirconium chloride;-   bis(cyclopentadienyl)benzylzirconium chloride;-   bis(cyclopentadienyl)zirconium chloride monohydride;-   bis(cyclopentadienyl)hafnium chloride monohydride;-   bis(cyclopentadienyl)methylzirconium hydride;-   bis(cyclopentadienyl)dimethylzirconium;-   bis(cyclopentadienyl)dimethylhafnium;-   bis(cyclopentadienyl)diphenylzirconium;-   bis(cyclopentadienyl)dibenzylzirconium;-   bis(cyclopentadienyl)methoxyzirconium chloride;-   bis(cyclopentadienyl)ethoxyzirconium chloride;-   bis(cyclopentadienyl)zirconium bis(methanesulfonate);-   bis(cyclopentadienyl)zirconium bis(p-toluenesulfonate);-   bis(cyclopentadienyl)zirconium bis(trifluoromethanesulfonate);-   bis(methylcyclopentadienyl)zirconium dichloride;-   bis(dimethylcyclopentadienyl)zirconium dichloride;-   bis(trimethylcyclopentadienyl)zirconium dichloride;-   bis(tetramethylcyclopentadienyl)zirconium dichloride;-   bis(pentamethylcyclopentadienyl)zirconium dichloride;-   bis(hexylcyclopentadienyl)zirconium dichloride;-   bis(dimethylcyclopentadienyl)ethoxyzirconium chloride;-   bis(dimethylcyclopentadienyl)zirconium    bis(trifluoromethanesulfonate);-   bis(ethylcyclopentadienyl)zirconium dichloride;-   bis(methylethylcyclopentadienyl)zirconium dichloride;-   bis(propylcyclopentadienyl)zirconium dichloride;-   bis(methylpropylcyclopentadienyl)zirconium dichloride;-   bis(n-butylcyclopentadienyl)zirconium dichloride;-   bis(n-butylcyclopentadienyl)hafnium dichloride;-   bis(methylbutylcyclopentadienyl)zirconium bis(methanesulfonate);-   bis(trimethylsilylcyclopentadienyl)zirconium dichloride;-   bis(n-butylcyclopentadienyl)hafnium monochloride monohydride;-   bis(n-butylcyclopentadienyl)zirconium monochloride monohydride;-   bis(cyclopentadienyl)hafnium dichloride;-   bis(cyclopentadienyl)dimethylhafnium;-   bis(n-butylcyclopentadienyl)zirconium dichloride;-   bis(n-butylcyclopentadienyl)dimethylzirconium;-   bis (n-butylcyclopentadienyl)dimethylhafnium;-   bis(pentamethylcyclopentadienyl)hafnium dichloride;-   bis(n-propylcyclopentadienyl)zirconium dichloride;-   bis(n-propylcyclopentadienyl)dimethylzirconium;-   bis(1,3-methyl-butyl-cyclopentadienyl)zirconium dichloride;-   bis(1,3-methyl-butyl-cyclopentadienyl)dimethylzirconium; and-   cyclopentadienylzirconium trichloride.

Of these, bis(cyclopentadienyl)zirconium dichloride andbis(n-butylcyclo-pentadienyl) zirconium dichloride are preferredmetallocene components for use in the present invention.

Of course, mixtures of metallocene components may also be used andgenerally, no restrictions are imposed on the metallocene componentswhich may be included. Any metallocene component that may be used alonemay also be used in conjunction with other metallocene components.Moreover, as already explained above the amount of metallocenecomponent(s) employed is such that it results in the desired ratio ofHMW polymer component to LMW polymer component in the polyethylene resinwith a bimodal MWD to be produced, which ratio in turn is at least inpart determined by the atomic ratio of metal(s) of the non-metallocenetransition metal component(s) to metal(s) of the metallocenecomponent(s). Generally the atomic ratio is at least about 1:1, morepreferably at least about 2:1 or at least about 3:1, and most preferredat least about 4:1. On the other hand the ratio is generally not higherthan about 30:1, preferably not higher than about 15:1, with a ratio ofnot higher than about 10:1 being particularly preferred.

Incorporation of the metallocene catalyst component into the carrier canbe accomplished in various ways. Incorporation of either or both thealuminoxane and the metallocene component can be into a slurry ofcatalyst intermediate in a non-polar solvent. The aluminoxane andmetallocene component can be added in any order, or together (e.g., assolution in an aromatic or the same non-polar solvent), to that slurryor to the isolated catalyst intermediate. A preferred way of combiningaluminoxane and metallocene is to add a solution of these two componentsin an aromatic solvent (preferably toluene) to a slurry of the catalystintermediate in a different non-polar solvent. This is preferably doneat room temperature, but higher temperatures can also be used as long asthe stability of the various materials present is not affected thereby.

Following the addition, the resulting mixture is usually stirred(preferably at room temperature) for sufficient time to allow all of thecomponents to react and/or interact substantially completely with eachother. Generally the resulting mixture is stirred for at least about 0.5hours, preferably at least about 1.0 hours, while stirring times inexcess of about 10 hours usually do not offer any particular advantage.Thereafter, the liquid phase can be evaporated from the slurry toisolate a free-flowing powder containing both non-metallocene andmetallocene transition metal components. Filtering is usually avoided tosubstantially eliminate the loss of catalytic components. If evaporationof the liquid phase under atmospheric pressure would requiretemperatures that might adversely affect the catalyst components(degradation) reduced pressure may be used.

As mentioned above, preferably the catalyst intermediate is firstrecovered from the slurry in the initially employed non-polar solvent orsolvent mixture (e.g., by filtration and/or distilling the solvent) andis then reslurried in the same or a different non-polar solvent.Non-limiting examples of suitable non-polar solvents for the abovepurpose (i.e., reslurrying of catalyst intermediate) include, but arenot limited to, aliphatic, cycloaliphatic and aromatic hydrocarbons suchas those set forth above for use in the preparation of the initialslurry of the support material in a non-polar solvent, e.g., n-pentane,isopentane, n-hexane, methylcyclopentane isohexane, cyclohexane,n-heptane, methylcyclohexane, isoheptane, benzene, toluene,ethylbenzene, xylenes and mixtures of two or more thereof.

The aluminoxanes to be employed according to the present invention arenot particularly limited. They include oligomeric linear and/or cyclicalkylaluminoxanes of the general formula R—(Al(R)—O)_(n)—AlR₂ foroligomeric, linear aluminoxanes and (—Al(R)—O—)_(m) for oligomericcyclic aluminoxanes, wherein n is 1-40, preferably 10-20, m is 3-40,preferably 3-20, and R is a C₁-C₈ alkyl group, and preferably methyl toprovide methylaluminoxane (MAO). MAO is a mixture of oligomers with avery wide distribution of molecular weights and usually with an averagemolecular weight of about 1200. MAO is typically kept in solution intoluene. It is also possible to use, for the present purpose,aluminoxanes of the type just described wherein the alkyl groups in theabove general formulae are different. A preferred example thereof ismodified methylaluminoxane (MMAO) wherein in comparison to MAO a part ofthe methyl groups is replaced by other alkyl groups. Modifiedmethylaluminoxanes are disclosed, e.g, in U.S. Pat. No. 6,001,766, thedisclosure of which is expressly incorporated by reference herein in itsentirety.

The aluminoxane or mixture of aluminoxanes is employed in an amountwhich results in sufficient activation of (at least) the metallocenetransition metal catalyst component of the bimetallic catalyst of thepresent invention. Because the metallocene transition metal catalystcomponent of the bimetallic catalyst produces the LMW polymer componentof the polyethylene resin to be made therewith, under otherwiseidentical polymerization conditions the weight fraction of LMW polymercomponent usually increases with increasing amount of aluminoxaneemployed. Generally, the atomic ratio of Al in the aluminoxane to metalin the metallocene component(s) is at least about 10:1, more preferablyat least about 50:1, and most preferred at least about 80:1. On theother hand said ratio is generally not higher than about 1,000:1,particularly not higher than about 500:1, with a ratio of not higherthan about 300:1 being particularly preferred.

An alternative way of incorporating the aluminoxane or the activatedmetallocene catalyst component (metallocene-aluminoxane) onto thesupport is by stripping the catalyst intermediate of the solvent to forma free-flowing powder. This free-flowing powder can then be impregnatedby determining the pore volume of the intermediate material andproviding an aluminoxane (or metallocene-aluminoxane) solution in avolume equal to or less than two times the total pore volume of theintermediate material, whereafter the dry bimetallic catalyst isrecovered. A more detailed description of said impregnation(incorporation) procedure can be found in, e.g, U.S. Pat. No. 5,614,456,discussed above.

The bimetallic catalyst according to the present invention can beemployed as such (i.e., without any activator or cocatalyst) for theproduction of bimodal polyethylene resins. The reason therefor is thatthe aluminoxane used in the preparation of the bimetallic catalystactivates not only the metallocene catalyst component but also (at leastto some extent) the non-metallocene catalyst component. The purpose ofthe additional (and optional) cocatalyst is to control the relativeactivity of said two catalyst components, i.e., the amount of polymerproduct produced by each of the two catalyst components, and thus theratio of HMW polymer component to LMW polymer component. Consequently,if the latter ratio as afforded by the instant bimetallic catalystwithout cocatalyst is acceptable for the intended purpose, a cocatalystneed not be employed. Generally, however, it is preferred to use thebimetallic catalyst of the present invention in combination with acocatalyst (that primarily activates the non-metallocene catalystcomponent) to form a catalyst composition suitable for the production ofhomo- and copolymers of ethylene with a controlled bimodal molecularweight distribution in a single reactor.

Suitable cocatalysts are organometallic components of Group IA, IB, IIA,IIB, IIIA or IIIB elements, such as, e.g, aluminum, sodium, lithium,zinc, boron and magnesium, and in general any one or a combination ofany of the materials commonly employed to activate Ziegler-Natta olefinpolymerization catalyst components. Examples thereof are alkyls,hydrides, alkylhydrides and alkylhalides of the mentioned elements, suchas n-butyllithi{umlaut over (um)}, diethylzinc, di-n-propylzinc andtriethylboron. Usually, however, the cocatalyst will be an alkylaluminumcomponent, preferably a compound of the general formula (IV):R⁵SAIXb   (IV)wherein a is 1, 2 or 3, R⁵ is a linear or branched alkyl groupcontaining 1 to about 10 carbon atoms, X represents hydrogen atom orhalogen atom and b is 0, 1 or 2, provided that the sum (a+b) is 3.

Preferred types of compounds of the general formula (IV) above aretrialkylaluminum, dialkylaluminum hydride, dialkylaluminum halide,alkylaluminum dihydride and alkylaluminum dihalide. The halidepreferably is Cl and/or Br. Preferred alkyl groups are linear orbranched and contain 1 to about 6 carbon atoms, such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, straight-chain and branched pentyland hexyl groups. Specific examples of suitable cocatalysts aretrimethylaluminum, triethylaluminum, tripropylaluminum,triisopropylaluminum, tributylaluminum, triisobutylaluminumtrihexylaluminum, trioctylaluminum diisobutylhexylaluminumisobutyldihexylaluminum diisobutylaluminum hydride, dihexylaluminumhydride, diethylaluminum chloride, and diisobutylaluminum chloride. Apreferred cocatalyst is trimethylaluminum (TMA). Other alkylaluminumcomponents, for example those wherein X in the above formula (IV) isalkoxy (e.g., having 1 to 6 carbon atoms) may also be employed.

The amount of cocatalyst is sufficient to (further) activate thenon-metallocene transition metal component of the bimetallic catalyst. Asuitable amount can be determined by one of ordinary skill in the art.If too little cocatalyst is used, the catalyst may not be completelyactivated, leading to wasted non-metallocene transition metal componentof the catalyst and also failing to provide the target ratio of HMWpolymer component to LMW polymer component in the polyethylene resin tobe produced (provided the metallocene component of the catalystprecursor is fully activated by the aluminoxane component). Too muchcocatalyst, on the other hand, results in wasted cocatalyst, and mayeven comprise an unacceptable impurity in the polymer produced.Generally, however, the amount of cocatalyst employed is based on theamount of ethylene fed to the polymerization process. The amount ofcocatalyst generally is at least about 5 ppm, more preferably at leastabout 20 ppm, and most preferably at least about 40 ppm. On the otherhand, the amount of cocatalyst generally is not higher than about 500ppm, preferably not higher than about 400 ppm and particularly nothigher than about 300 ppm (based on the ethylene employed).

Polymerization

The catalyst or catalyst composition, respectively, of this invention isused to polymerize either ethylene alone or ethylene in conjunction withother olefin-based monomers, such as one or more higher olefins.Examples thereof are C₃-C₁₀ α-olefins, e.g., propylene, 1-butene,1-pentene, 1-hexene, 4-methyl-l -pentene, 1-heptene and 1-octene,preferably 1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene and mostpreferably 1-hexene. The polymerization may be carried out using anysuitable, conventional olefin polymerization process, such as slurry,solution or gas phase polymerization but preferably it is carried out ina slurry reactor or in a gas phase reactor, particularly a fluidized-bedreactor. The polymerization can be carried out batchwise,semicontinuously or continuously. The reaction is conducted in thesubstantial absence of catalyst poisons, such as moisture, carbonmonoxide and acetylene, with a catalytically effective amount of thecatalyst (composition) at temperature and pressure conditions sufficientto initiate the polymerization reaction. Particularly desirable methodsfor producing the polymers of the present invention are in a slurry orfluidized-bed reactor. Such reactors and means for operating them aredescribed by, e.g. Levine et al., U.S. Pat. No. 4,001,382, Karol et al.,U.S. Pat. No. 4,302,566, and Nowlin et al., U.S. Pat. No. 4,481,301, theentire contents of which are expressly incorporated herein by reference.The polymer produced in such reactors contains (deactivated) catalystparticles because the catalyst is not separated from the polymer.

With the catalysts according to the present invention, molecular weightof the polymer may be suitably controlled in a known manner, e.g., byusing hydrogen. Hydrogen acts as chain transfer agent. Other reactionconditions being the same, a greater amount of hydrogen results in alower average molecular weight of the polymer. The molar ratio ofhydrogen/ethylene employed will vary depending on the desired averagemolecular weight of the polymer, and can be determined by a person ofordinary skill in the art for each particular instance. Without limitingthe present invention, the amount of hydrogen will generally be betweenabout 0 to about 2.0 moles of hydrogen per mole of ethylene.

Polymerization temperature and time can be determined by one of ordinaryskill in the art based on a number of factors, such as the type ofpolymerization process to be used and the type of polymer to beprepared.

As chemical reactions generally proceed at a greater rate with highertemperature, polymerization temperature should be high enough to obtainan acceptable polymerization rate. In general, therefore, polymerizationtemperatures are higher than about 30° C., more often higher than about75° C. On the other hand, polymerization temperature should not be sohigh as to cause deterioration of, e.g., catalyst or polymer.Specifically, with respect to a fluidized-bed process, the reactiontemperature is preferably not so high as to lead to sintering of polymerparticles. In general, polymerization temperatures are less than about300° C., preferably less than about 115° C., more preferably less thanabout 105° C.

The polymerization temperature used in the process is in part determinedby the density of the polyethylene resin to be produced. Moreparticularly, the melting point of the resin depends on resin density.The higher the density of the resin, the higher its melting point.Therefore, lower density resins are produced at lower temperatures toavoid melting or sintering of the polymer particles being produced inthe reactor. Thus, without limiting the present invention, polyethyleneresins having densities below about 0.92 g/cm³ are polymerized at atemperature preferably above about 60° C., but preferably below about90° C. Polyethylene resins having densities of about 0.92 to about 0.94g/cm³ are polymerized at a temperature preferably above about 70° C.,but preferably below about 100° C. Polyethylene resins having densitiesabove about 0.94 g/cm³ are polymerized at a temperature preferably aboveabout 80° C., but preferably below 115° C.

When a fluidized-bed reactor is used, a person of ordinary skill in theart is readily able to determine appropriate pressures to use.Fluidized-bed reactors can be operated at pressures of up to about 1000psi (6.9 MPa) or more, and are generally operated at pressures belowabout 350 psi (2.4 MPa). Preferably, fluidized-bed reactors are operatedat pressures above about 150 psi (1.0 MPa). As is known in the art,operation at higher pressures favors heat transfer because an increasein pressure increases the unit volume heat capacity of the gas.

Once the catalyst is activated, the activated catalyst has a limitedlifetime before it becomes deactivated. As is known to those of ordinaryskill in the art, the half-life of an activated catalyst depends on anumber of factors, such as the species of catalyst (and cocatalyst), thepresence of impurities (e.g., water and oxygen) in the reaction vessel,and other factors. An appropriate length of time for carrying out apolymerization can be determined by a person skilled in the art for eachparticular situation.

The density of ethylene copolymers is in part determined by the amountof comonomer(s) in the polymer molecule. In order to achieve densityranges from about 0.915 to about 0.970 g/cm³ in the copolymers, it isnecessary to copolymerize enough α-olefin comonomer with ethylene toachieve a level of about 0.1 to about 25 mole percent of thecomonomer(s) in the copolymer. The amount of comonomer needed to achievethis result will depend on the particular comonomer(s) being employed.Further, the various intended comonomers have different reactivityrates, relative to the reactivity rate of ethylene, with respect to thecopolymerization thereof with the catalysts of the present invention.Therefore the amount of comonomer fed to the reactor will also varydepending on the reactivity of the comonomer.

According to the present invention, it is highly preferred to polymerizeethylene and one α-olefin, particularly 1-hexene, to obtain copolymershaving a density of at least about 0.915 g/cm³, more preferably at leastabout 0.930 g/cm³, but usually not higher than about 0.970 g/cm³,particularly not higher than about 0.960 g/cm³. The flow index (FI) ofthe copolymers is preferably at least about 1 g/10 mm, more preferablyat least about 3 g/10 mm, but preferably not higher than about 100 g/10mm, and particularly not higher than about 80 g/10 mm. The annular dieswell at a shear rate of 210^(s−1) of the copolymers preferably is notlower than about 0.3 g, particularly not lower than about 0.35 g, butpreferably not higher than about 0.50 g, particularly not higher thanabout 0.46 g, whereas their annular die swell at a shear rate of6300^(s−1) preferably is not lower than about 0.55 g, particularly notlower than about 0.68 g, but preferably not higher than about 0.95 g,particularly not higher than about 0.88 g. The polyethylene resins ofthe present invention are especially suitable for the manufacture ofblow molded articles, e.g., bottles.

In general, the polyethylene resins of the present invention arepreferably extruded or injection or blow molded into articles orextruded or blown into films. For example, films can be produced whichare about 0.2 to 5.0 mils (5 to 130 μm, preferably about 0.5 to 2.0 mils(10 to 50 μm) in thickness. Blow molded articles include bottles,containers, fuel tanks and drums. The wall thickness of the blow moldedarticles will usually be in the range from about 0.5 to about 2,000 mils(10 μm to 50 mm).

The present polymers may be combined with various additivesconventionally added to polymer compositions, such as lubricants,fillers, stabilizers, antioxidants, compatibilizers, pigments, etc. Manyadditives can be used to stabilize the products. For example, additivepackages comprising hindered phenol(s), phosphites, antistats andstearates, for addition to resin powders, can be used for pelletization.

EXAMPLES

Methods and Materials

The following Examples further illustrate the essential features of thepresent invention. However, it will be apparent to those skilled in theart that the specific reactants and reaction conditions used in theExamples do not limit the scope of the present invention.

The properties of the polymers produced in the Examples were determinedas follows:

Analysis of the Resin Produced:

Prior to testing, the polymers were processed as described below.

Additives: 1000 ppm each of 1rganox™ 1010 (hindered phenol antioxidant)and 1rgafos™ 168 (phosphite antioxidant), both produced by C.K. WitcoCorp., and 500 ppm of AS900 (antistatic agent manufactured byCiba-Geigy, Switzerland), were dry blended with the granular resin. Themixture was then melt mixed using either a Brabender twin screwcompounder (¾″ (19 mm) screw diameter) at melt temperatures of less than200° C., with a nitrogen purge to the feed throat, or a 40 g Brabenderbatch mixer.

Flow Index: The Flow Index (FI, g/10 mm, at 190° C. was determined asspecified in ASTM D 1238 using a load of 21.6 kg.

Density: The density (g/cm³) was determined as specified in ASTM D1505-68 with the exception that the density measurement was taken 4hours instead of 24 hours after the sample was placed in the densitycolumn.

Die Swell: Die swell was measured by a technique outlined in theProceedings of the SPE 48th Annual Technical Conference, 1990, pp.1612-1616, the disclosure of which is expressly incorporated herein byreference in its entirety. This test determines the weight of an annularextrudate under controlled extrusion conditions. The test is conductedat a range of shear rates, generally 210^(s−1) to 6300^(s−1), theseshear rates being typical of those used in commercial blow moldingoperations. The weight of the extrudate relates to the bottle wallthickness, and bottle weight. Annular die swell measurements have anexcellent correlation to bottle weight.

Analytical procedure for resolving components in bimodal polyethyleneresins:

Studies of bimetallic catalysts used for the synthesis of bimodalpolyethylene resins utilized Gel Permeation Chromatography (GPC) todetermine polymer molecular weight distribution (MWD). The molecularweight characterization given in the following Examples was carried outon a Waters 150C gel permeation chromatograph. The chromatograms wererun at 140° C. using 1,3,5-trichlorobenzene as the solvent. The Waters150C determines MWD using the technique of size exclusion. The molecularweight data were used to determine the number average molecular weight(M_(n)) and the weight average molecular weight (M_(w)), and fordeconvolution of the bimodal MWD resins into the separate low molecularweight (LMW) and high molecular weight (HMW) polymer components.

In a typical GPC curve of the bimodal PE resin, the contributions fromeach molecular weight polymer component overlap significantly. Thisresults in a broad GPC chromatogram with relatively poor resolution ofeach of the two polymer components, i.e., the relatively high molecularweight component and the relatively low molecular weight component.

To overcome this problem, resin samples were produced using singlecomponent catalysts in which the catalyst formulation was chosen toattempt to match either the Zr catalyst component (producing the LMWpolymer component) or the Ti catalyst component (producing the HMWpolymer component) in the bimetallic Ti/Zr catalyst. Each GPC curve wasresolved into Flory peaks according to the earlier described procedure(V. V. Vickroy, H. Schneider and R. F. Abbott, J., Appl. Polym. Sci.,50, 551 (1993); Y. V. Kissin, J. Poly Sci., Part A, Polym. Chem., 33,227 (1995); Y. V. Kissin, Makromol. Chem., Macromol. Symp., 66. 83(1993)). One Flory peak represents the polymer produced by only one typeof active site in the catalyst. Hence, resolution of the polymer sampleinto individual Flory components ascertains the number of individualactive sites in the catalyst that provided the polymer sample.

For example, the LMW polyethylene produced by only the Zr catalystcomponent is represented by three Flory peaks (one low molecular weightpeak present in very small quantity and two somewhat higher molecularweight peaks in similar quantities). The HMW polymer component (producedby only the Ti catalyst component) can be described as an overlap ofeither four or five Flory peaks. Four Flory peaks are required to modelthe polyethylene produced by a Ti-based catalyst component wherein theintermediate has been treated with 1-butanol, while five Flory peaks arerequired to model the polyethylene produced by Ti-based catalystcomponents prepared with the aldehyde/ketone treated intermediate.

To avoid uncertainties caused by the significant overlap of the highestmolecular weight Flory peak of the polyethylene produced by the Zr-onlycatalyst component and the two relatively lower molecular weight Florypeaks of the HMW polymer components, a computer analysis procedure wasdeveloped. This procedure uses the relationship between respective peakpositions in the single-catalyst component polymer samples and otherFlory peaks that do not overlap in the GPC curves of the same resins.This procedure affords a reliable estimation of the amount of polymerproduced from each of the two catalyst components. It also allowscalculation of the average molecular weights of the LMW and the HMWpolymer components as well as their molecular weight distributions.

Catalyst Preparation Example 1

Under a dry nitrogen atmosphere, a Schlenk flask was charged with silica(Davison 955, 6.00 g), previously calcined at 600° C. for 4 hours, andisohexane (about 100 mL). The flask was placed into an oil bath (about55° C.). Dibutylmagnesium (4.32 mmol) was added to the stirred silicaslurry at about 55° C. and stirring was continued for about 1 hour.Then, benzaldehyde (4.32 mmol, molar ratio magnesiumcompound:carbonyl-containing component=1:1) was added to the flask atabout 55° C. and the mixture was stirred for about 1 hour. Finally,TiCI₄ (2.592 mmol, atomic ratio Mg:Ti=1.67:1) was added at about 55° C.and stirring was continued for about 1 hour. The liquid phase wasremoved by evaporation under nitrogen flow at about 55° C. to yield afree-flowing powder. A portion of this powder (2.00 g) was thenre-slurried in isohexane (about 50 mL) at ambient temperature. Then, asolution prepared by combining bis(n-butylcyclopentadienyl)zirconiumdichloride ((n-BuCp)₂ZrCl₂, 0.10 mmol, 0.0404 g, atomic ratioTi:Zr=7.4:1) with MAO (methylaluminoxane) (12.00 mmol Al, atomic ratioAl:Zr=120:1) in toluene was added to the slurry. After stirring theresulting mixture at ambient temperature for about 0.5 hours, the liquidphase was removed by evaporation under a dry nitrogen flow at about 55°C. to yield a free-flowing powder. In this catalyst powder, the Zrcatalyst component is completely activated by the MAO and is capable ofproducing polyethylene without the addition of any other cocatalyst. Inaddition, the MAO also activates the Ti catalyst component relativelywell so that the Ti catalyst component can also produce polyethylene.The use of an additional cocatalyst together with this catalyst,therefore, only serves to control the relative reactivities of these twocatalyst components (and, thus, the relative ratio of HMW polymercomponent and LMW polymer component produced by the bimetalliccatalyst).

Catalyst Preparation Example 2

Catalyst Preparation Example 1 was repeated, except that salicylaldehyde(4.32 mmol) was used in place of benzaldehyde.

Catalyst Preparation Example 3

Catalyst Preparation Example 1 was repeated, except that butyraldehyde(4.32 mmol) was used in place of benzaldehyde.

Catalyst Preparation Example 4

Catalyst Preparation Example 1 was repeated, except that 2-pentanone(4.32 mmol) was used in place of ben.zaldehyde.

Catalyst Preparation Example 5

Catalyst Preparation Example 1 was repeated, except that3′-methylacetophenone (4.32 mmol) was used in place of benzaldehyde.

Catalyst Preparation Example 6

Under a dry nitrogen atmosphere, a Schlenk flask was charged with silica(Davison 955, 6.00 g), previously calcined for 4 hours at 600° C., andisohexane (about 100 mL). The flask was placed in an oil bath (about 55°C.). Dibutylmagnesium (4.32 mmol) was added to the stirred silica slurryat about 55° C. and stirring was continued for about 1 hour. Then,benzaldehyde (4.32 mmol) was added to the flask at about 55° C. and themixture was stirred for about 1 hour. Finally, TiCl₄ (2.592 mmol) wasadded to the flask at about 55° C. and stirring was continued for about1 hour. The liquid phase was removed by evaporation under dry nitrogenflow at about 55° C. to yield a free-flowing powder. A portion of thispowder (2.00 g) was then re-slurried in isohexane (about 50 mL) atambient temperature. Then, a solution prepared by combiningbis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂, 0.14 mmol. 0.0409g) with MAO (14.00 mmol Al) in toluene was added to the slurry. Afterstirring the resulting mixture at ambient temperature for about 0.5hours, the liquid phase was removed by evaporation under a dry nitrogenflow at about 55° C. to yield a free-flowing powder.

Catalyst Preparation Example 7

Catalyst Preparation Example 6 was repeated, except that the MAO andCp₂ZrCl₂, loadings were decreased to 12,00 mmol Al and 0.12 mmol (0.0351g), respectively.

Catalyst Preparation Example 8

Catalyst Preparation Example 6 was repeated, except that the TiCl₄loading was increased from 2.592 mmol to 3.06 mmol.

Catalyst Preparation Example 9

Catalyst Preparation Example 7 was repeated, except that the TiCI₄loading was increased from 2.592 mmol to 3.06 mmol.

Catalyst Preparation Example 10

Catalyst Preparation Example 7 was repeated, except that the TiCl₄loading was increased from 2.592 mmol to 3.66 mmol.

Catalyst Preparation Example 11

Catalyst Preparation Example 6 was repeated, except that3′-methylacetophenone (4.32 mmol) was used in place of benzaldehyde.

Catalyst Preparation Example 12

Catalyst Preparation Example 6 was repeated, except that p-tolualdehyde(4.32 mmol) was used in place of benzaldehyde.

Catalyst Preparation Example 13

Catalyst Preparation Example 12 was repeated, except that the TiCl₄loading was increased from 2.592 mmol to 3.66 mmol.

Polymerization Examples 1-13

Ethylene/1-hexene copolymers were prepared in a slurry polymerizationprocess with the bimetallic catalysts prepared according to CatalystPreparation Examples 1-13 in the presence of trimethylaluminum (TMA)cocatalyst.

A 1.6 liter stainless-steel autoclave equipped with a magnet-driveimpeller stirrer was filled with heptane (750 mL) and 1-hexene (30 mL)under a slow nitrogen purge at 50° C. and then TMA (2.0 mmol) was added.The reactor vent was closed, the stirring speed was increased to 1000rpm, and the temperature was increased to 95° C. The internal pressurewas increased by 6.0 psi (41 kpa)with hydrogen and then ethylene wasintroduced to maintain the total pressure at 200-210 psig (1.4-1.5 MPa).After that, the temperature was decreased to 85° C., 20.0-40.0 mg of thecatalyst was introduced into the reactor with ethylene overpressure, andthe temperature was increased and held at 95° C. The polymerizationreaction was carried out for 1 hr and then the ethylene supply wasstopped. The reactor was cooled to ambient temperature and thepolyethylene was collected. The polymerization results are given inTable 1. Catalyst Ti Al Prep. Loading Loading Productivity Flow IndexExample Modifier (mmol)* (mmol)** (g/g · hr) (g/10 mm) 1 Benzaldehyde2.592 12.00 2390 52.6 2 Salicylaldehyde 2.592 12.00 880 4.5 3Butyraldehyde 2.592 12.00 1160 55.1 4 2-Pentanone 2.592 12.00 1650 4.7 53′-Methyl-acetophenone 2.592 12.00 1840 130 6 Benzaldehyde 2.592 14.001600 35.5 7 Benzaldehyde 2.592 12.00 1350 21.1 8 Benzaldehyde 3.06 14.001560 17.6 9 Benzaldehyde 3.06 12.00 1490 12.9 10 Benzaldehyde 3.66 12.002420 5.4 11 3′-Methyl-acetophenone 2.592 12.00 1210 6.0 12p-Tolualdehyde 2.592 14.00 1640 44.9 13 p-Tolualdehyde 3.66 14.00 26604.7*mmol/6.00 g silica**mmol/2.00 g Ti intermediate

The F1 value given in Table 1 is directly proportional to the amount ofLMW polymer component produced by the Zr catalyst component. Low FIvalues indicate that the polymer produced with the bimetallic catalysthas a relatively small amount of LMW polymer component.

As can be seen from the results in Table 1, the relative fraction of lowand high molecular weight components in the bimodal resins produced bythe Ti/Zr bimetallic catalysts according to the present inventiondepends upon the modifier type (identity of aldehyde/ketone), Ti loadingand Al loading used in the preparation of the catalyst. For a givenmodifier and Ti loading, increasing the Al loading in the preparation ofthe catalyst results in resins with a higher weight fraction of the lowmolecular weight component (produced by the Zr active centers), asevident from GPC curve (FIG. 1), and a higher flow index of the resin.Moreover, the MWD of the HMW polymer component and the molecular weightof the LMW polymer component can be varied by changing the catalystpreparation modifier (carbonyl-containing component).

Comparative Catalyst Preparation Example 1

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (Davison 955,367 g), previously calcined for 4 hours at 600° C. under dry nitrogen,and isohexane (3600 mL) were added to a 2 gallon (7.6 L) glass vesselcontaining a stirring paddle. The stirring rate was set to 100 rpm, andthe temperature of the silica/isohexane slurry was raised to 51-54° C.for the following reagent addition and drying steps. Next,dibutylmagnesium (0.264 mol, 265.3 g of a 2.42 wt % Mg solution inheptane) was added to the stirred silica slurry. After stirring at51-54° C. for 2 hours, 1-butanol (0.251 mol, 1 8.6 g) was added to thestirred reaction mixture. After stirring for another two hours, titaniumtetrachloride (0.160 mol, 30.3 g) was added to the stirred reactionmixture, and stirring was continued for 2 hours. The liquid phase wasthen removed by evaporation under nitrogen purge, to yield afree-flowing powder.

STEP 2: Under an inert atmosphere of dry nitrogen and at ambienttemperature, 374 g of the titanium-containing catalyst componentdescribed in Step 1 above, and isopentane (1870 mL) were added to a 2gallon (7.6 L) glass vessel containing a stirring paddle. The stirringrate was set to 110 rpm. A solution was prepared by mixing(n-BuCp)₂ZrCl₂ (bis(n-butylcyclopentadienyl)zirconium dichloride) (21.2mmol, 8.564 g) and MAO (2.546 mol, 512.7 g of a 13.4 wt % Al solution intoluene) in a stainless-steel Hoke bomb at ambient temperature, under aninert atmosphere of dry nitrogen. This solution was then slowly added tothe stirred titanium catalyst component/isopentane slurry at ambienttemperature, over a period of 50 minutes. The temperature of thereaction mixture was raised to 47° C., and the liquid phase was removedby evaporation under nitrogen purge to yield a free-flowing brownpowder.

Comparative Catalyst Preparation Example 2

The catalyst is prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (Davison 955,432 g), previously calcined for 4 hours at 600° C. under dry nitrogen,and isohexane (2160 mL) were added to a 2 gallon (7.6 L) glass vesselcontaining a stirring paddle. The stirring rate was set to 100 rpm, andthe temperature of the silica/isohexane slurry was raised to 45-51° C.for the following reagent addition and drying steps. Next,dibutylmagnesium (0.309 mol, 205 g of a 3.67 wt % Mg solution inheptane) was added to the stirred silica slurry. After stirring at about50° C. for 1 hour, 1-butanol (0.297 mol, 22 g) was added to the stirredreaction mixture. After stirring for another hour, titaniumtetrachloride (0.113 mol, 21.4 g) was added to the stirred reactionmixture, and stirring was continued for 1 hour. The liquid phase wasthen removed by evaporation under nitrogen purge, to yield afree-flowing beige powder.

STEP 2: Under an inert atmosphere of dry nitrogen and at ambienttemperature, 330 g of the titanium-containing catalyst componentdescribed in Step 1 above, and isohexane (1650 mL) were added to a 2gallon (7.6 L) glass vessel containing a stirring paddle. The stirringrate was set to 120 rpm. A solution was prepared by mixing Cp₂,ZrCl₂(zirconocene dichloride) (26.5 mmol, 7.74 g) and MAO (2.64 mol Al, 532 gof a 13.4 wt % Al solution in toluene) in a stainless-steel Hoke bomb atambient temperature, under an inert atmosphere of dry nitrogen. Thissolution was then added to the stirred titanium catalystcomponent/isohexane slurry at ambient temperature, over a period of 30minutes. The temperature of the reaction mixture was raised to 48-50°C., and the liquid phase was removed by evaporation under nitrogen purgeto yield a free-flowing brown powder.

Catalyst Preparation Example 14

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen. silica (Davison 955,6.00 g), previously calcined for 4 hours at 600° C. under dry nitrogen,and isohexane (100 mL) were added to a Schlenk flask containing amagnetic stirring bar. The flask was placed in a 55° C. oil bath, andthe slurry was stirred vigorously. Next, dibutylmagnesium (4.32 mmol,5.45 mL of a 0.792 M solution in heptane) was added via syringe to thestirred silica slurry at 55° C. After stirring at 55° C. for 1.5 hours,benzaldehyde (4.32 mmol, 0.44 mL) was added via syringe to the stirredreaction mixture. After stirring at 55° C. for another 1.5 hours,titanium tetrachloride (3.06 mmol, 3.42 mL of a 0.894 M solution inheptane) was added via syringe to the stirred reaction mixture, andstirring was continued for 1 hour at 55° C. The liquid phase was thenremoved by evaporation under nitrogen purge at 55° C., to yield afree-flowing pale yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 2.0 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (50 mL) were added to a Schlenk flask containing a magneticstirring bar. A solution was prepared by mixing Cp₂ZrCl₂ (0.33 mmol,0.097 g) and MAO (33.2 mmol Al, 7.0 mL of a 4.74 M solution in toluene)in a serum bottle at ambient temperature, under an inert atmosphere ofdry nitrogen. Then 2.5 mL of this solution were added dropwise to thestirred titanium catalyst component/isohexane slurry at ambienttemperature. After stirring for another 75 minutes at ambienttemperature, the flask was placed in an oil bath and the liquid phasewas removed by evaporation under nitrogen purge at 57-59° C., to yield afree-flowing brown powder.

Catalyst Preparation Example 15

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (CrosfieldES70, 240 g), previously calcined for 4 hours at 600° C. under drynitrogen, and isohcxane (1440 mL) were added to a 3 liter round-bottomflask fitted with a paddle stirrer. The flask was placed in a 54° C. oilbath, and the slurry was stirred vigorously. Next, dibutylmagnesium(0.173 mol, 164 mL of a 1.05 M solution in heptane) was added dropwiseto the stirred silica slurry at 54° C. over 45 minutes. After stirringat 54° C. for another 45 minutes, benzaldchyde (0.173 mol, 18.3 g,diluted with 70 mL isohexane) was added dropwise to the stirred reactionmixture over 10 minutes. After stirring at 54° C. for another 45minutes, titanium tetrachloride (0.123 mol, 23.4 g, diluted with 70 mLisohexane) was added dropwise to the stirred reaction mixture, andstirring was continued for 45 minutes at 55° C. The liquid phase wasthen removed by evaporation under nitrogen purge at 54° C., to yield afree-flowing yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 272 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (1360 mL) were added to a 3 liter round-bottom flask fittedwith a paddle stirrer. The flask was placed in a 54° C. oil bath, andthe slurry was stirred vigorously. A solution was prepared by mixingCp₂ZrCl₂, (15.9 mmol, 4.64 g) and MAO (1.90 mol Al, 383 g of a 13.4 wt %Al solution in toluene) in a Schlenk flask at ambient temperature, underan inert atmosphere of dry nitrogen. This solution was then addeddropwise to the stirred titanium catalyst component/isohexane slurry,which was kept at 54° C., over a period of 45 minutes. After stirringfor a further 20 minutes at 54° C., the liquid phase was removed byevaporation under nitrogen purge at 54° C., to yield a free-flowingbrown powder.

Catalyst Preparation Example 16

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (CrosfieldES70, 130 g), previously calcined for 4 hours at 600° C. under drynitrogen, and isohexane (780 mL) were added to a 2 liter round-bottomflask fitted with a paddle stirrer. The flask was placed in a 54° C. oilbath, and the slurry was stirred vigorously. Next, dibutylmagnesium(0.0936 mol, 89.1 mL of a 1.05 M solution in heptane) was added dropwiseto the stirred silica slurry at 54° C. over 20 minutes. After stirringat 54° C. for another 50 minutes, benzaldehyde (0.0936 mol, 9.93 g,diluted with 40 mL isohexane) was added dropwise to the stirred reactionmixture over 10 minutes. After stirring at 54° C. for another 50minutes, titanium tetrachloride (0.0663 mol, 12.6 g, diluted with 40 mLisohexane) was added dropwise to the stirred reaction mixture over 10minutes, and stirring was continued for minutes at 54° C. The liquidphase was then removed by evaporation under nitrogen purge at 54° C., toyield a free-flowing yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 139 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (700 mL) were added to a 3 liter round-bottom flask fittedwith a paddle stirrer. The flask was placed in a 54° C. oil bath, andthe slurry was stirred vigorously. A solution was prepared by mixingCP₂ZrCl₂ (8.11 mmol, 2.37 g) and MAO (0.97 mol Al, 196 g of a 13.4 wt %Al solution in toluene) in a Schlenk flask at ambient temperature, underan inert atmosphere of dry nitrogen. This solution was then addeddropwise to the stirred titanium catalyst component/isohexane slurry,which was kept at 54° C., over a period of 130 minutes. The liquid phasewas removed by evaporation under nitrogen purge at 54° C., to yield afree-flowing brown powder.

Catalyst Preparation Example 17

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (Davison 955,6.00 g), previously calcined for 4 hours at 600° C. under dry nitrogen,and isohexane (100 mL) were added to a Schlenk flask containing amagnetic stirring bar. The flask was placed in a 55° C. oil bath, andthe slurry was stirred vigorously. Next, dibutylmagnesium (4.32 mmol,5.45 mL of a 0.792 M solution in heptane) was added via syringe to thestirred silica slurry at 55° C. After stirring at 55° C. for 1.5 hours,benzaldehyde (4.32 mmol, 0.44 mL) was added via syringe to the stirredreaction mixture. After stirring at 55° C. for another 1.5 hours,titanium tetrachloride (3.06 mmol, 3.42 mL of a 0.894 M solution inheptane) was added via syringe to the stirred reaction mixture, andstirring was continued or 1 hour at 55° C. The liquid phase was thenremoved by evaporation under nitrogen purge at 55° C., to yield afree-flowing pale yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 1.50 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (13 mL) were added to a Schlenk flask containing a magneticstirring bar. A solution was prepared by mixing Cp₂ZrCl₂ (0.26 mmol,0.077 g) and MAO (31.5 mmol Al, 6.9 mL of a 4.56 M solution in toluene)in a serum bottle at ambient temperature, under an inert atmosphere ofdry nitrogen. Then, 2.3 mL of this solution were added dropwise to thestirred titanium catalyst component/isohexane slurry at ambienttemperature over a period of 2 minutes. After stirring for a further 15minutes at ambient temperature, the flask was placed in an oil bath andthe liquid phase was removed by evaporation under nitrogen purge at 50°C., to yield a free-flowing brown powder.

Catalyst Preparation Example 18

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (Davison 955,6.00 g), previously calcined for 4 hours at 600° C. under dry nitrogen,and isohexane (100 mL) were added to a Schlenk flask containing amagnetic stirring bar. The flask was placed in a 55° C. oil bath, andthe slurry was stirred vigorously. Next, dibutylmagnesium (4.32 mmol,5.45 mL of a 0.792 M solution in heptane) was added via syringe to thestirred silica slurry at 55° C. After stirring at 55° C. for 1 .5 hours,benzaldehyde (4.32 mmol, 0.44 mL) was added via syringe to the stirredreaction mixture. After stirring at 55° C. for another 1.5 hours,titanium tetrachloride (3.06 mmol, 3.42 mL of a 0.894 M solution inheptane) was added via syringe to the stirred reaction mixture, andstirring was continued for 1 hour at 55° C. The liquid phase was thenremoved by evaporation under nitrogen purge at 55° C., to yield afree-flowing pale yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 2.0 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (50 mL) were added to a Schlenk flask containing a magneticstirring bar. A solution was prepared by mixing Cp₂ZrCl₂ (0.33 mmol,0.097 g) and MAO (33.2 mmol Al, 7.0 mL of a 4.74 M solution in toluene)in a serum bottle at ambient temperature, under an inert atmosphere ofdry nitrogen. Then, 2.95 mL of this solution were added dropwise to thestirred titanium component/isohexane slurry at ambient temperature.After stirring for an additional 70 minutes at ambient temperature, theflask was placed in an oil bath and the liquid phase was removed byevaporation under nitrogen purge at 57-60° C., to yield a free-flowingbrown powder.

Comparative Polymerization Example 1

An ethylene/1-hexene copolymer was prepared with the catalyst preparedas described in Comparative Catalyst Preparation Example 1. Thepolymerization was conducted in a gas phase reactor operated in acontinuous mode which is run at 100.0° C., 356 psig (2.45 MPa) totalreactor pressure, and with the following partial pressures: 162 psi(1.12 MPa) ethylene, 28.0 psi (193 kPa) isopentane, 0.81 psi (5.6 kPa)1-hexene and 2.4 psi (17 kPa) hydrogen. The molar gas ratios were 0.00501-hexene/ethylene and 0.0149 hydrogen/ethylene with a residence time of2.67 hours. The cocatalyst trimethylaluminum (TMA) level was 128 ppm byweight based on the ethylene feed to the reactor and the water addbacklevel was 34 ppm by volume. The ppm values were based on ethylene feed.A total of 140 pounds (64 kg) was collected for sampling.

Comparative Polymerization Example 2

An ethylenc/1-hexene copolymer was produced with the catalyst preparedas described in Comparative Catalyst Preparation Example 2. Thepolymerization was conducted in a gas phase continuous reactor which wasrun at 100.0° C., 341 psig (2.35 MPa) total reactor pressure, and withthe following partial pressures: 197 psi (1.36 MPa) ethylene, 16.2 psi(112 kPa) isopentane, 1.60 psi (11.0 kPa) 1-hexene and 3.1 psi (21 kPa)hydrogen. The molar gas ratios were 0.0081 1-hexene/ethylene and 0.0158hydrogen/ethylene with a residence time of 4.36 hours. The cocatalysttrimethylaluminum (TMA) level was 24.5 ppm by weight, modifiedmethyl-aluminoxane (MMAO) was 137 ppm by weight, and no water addbackwas used. The ppm values are based on ethylene feed. A total of 241pounds (109 kg) of polyethylene was produced for product evaluation.

Polymerization Example 14

A 3.8 liter stainless steel autoclave operated in the batch mode,equipped with a paddle stirrer, under a slow nitrogen purge at 50° C.,and with stirring set to 300 rpm, was charged with 1500 mL of dryheptane, 40 μL of water (see explanation of the function of water at theend of this Example), 4.2 mmol (3.0 mL of a 1.4 M solution in heptane)of trimethylaluminum (TMA), and 60 mL of 1-hexene. The reactor vent wasclosed and the stirring speed set to 900 rpm, and the internaltemperature was raised to 95° C., whereafter the internal pressure wasraised from 11 psi (76 kPa) to 17 psi (117 kPa) by addition of 6 psi (41kPa) of hydrogen. Ethylene was then introduced into the reactor and theinternal pressure was increased to 224 psi (1.54 MPa). Finally, 0.0437 gof the catalyst prepared as described in Catalyst Preparation Example 14was added to the autoclave. The reactor pressure was maintained at219-224 psi (1.51-1.54 MPa) for 60 minutes by addition of ethylene,after which time the ethylene flow to the reactor was stopped and thereactor was cooled to room temperature and vented to the atmosphere. Thecontents of the autoclave were removed, and all solvents were removedfrom the product by evaporation, to yield 66.7 g of polyethylene resin(ethylene/I-hexene copolymer).

It is noted that the addition of very small amounts of water to apolymerization reactor containing TMA (or any other alkylaluminumcomponent) significantly increases the activity of the metallocenecatalyst component relative to the non-metallocene catalyst component.This water addition process is commonly referred to as ‘water addback.”Hence, water addback is a method of controlling the weight fractions ofthe HMW and LMW polymer components. This is an extremely importanttechnique in a commercial reactor to produce the target polyethylene.For example, if the product must contain 60% by weight HMW polymercomponent and 40% by weight LMW polymer component, water addback isnormally used to meet this product composition requirement. U.S. Pat.No. 5,525,678 to Mink et al., the disclosure of which is expresslyincorporated herein by reference in its entirety, discloses this wateraddback technique for controlling polymer weight fractions with abimetallic catalyst.

Polymerization Example 15

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,under a slow nitrogen purge at 50° C., and with stirring set to 300 rpm,was charged with 1500 Ml of dry heptane, 40 μL of water, 4.2 mmol (3.0mL of a 1.4 M solution in heptane) of trimethylaluminum (TMA), and 60 Mlof 1-hexene. The reactor vent was closed and the stirring speed set to900 rpm, and the internal temperature was raised to 95 2° C., whereafterthe internal pressure was raised from 10 psi (69 kPa) to 16 psi (110kPa) by addition of hydrogen. Ethylene was introduced into the reactorand the internal pressure was increased to 227 psi (1.57 MPa). Finally,0.0482 g of the catalyst prepared as described in Catalyst PreparationExample 15 was added to the autoclave. The reactor pressure wasmaintained at 220-225 psi (1.52-1.55 MPa) for 60 minutes by addition ofethylene, after which time the ethylene flow to the reactor was stoppedand the reactor was cooled to room temperature and vented to theatmosphere. The contents of the autoclave were removed, and all solventswere removed from the product by evaporation, to yield 88.8 g ofpolyethylene resin (ethylene/1-hexene copolymer).

Polymerization Example 16

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,under a slow nitrogen purge at 50° C., and with stirring set to 300 rpm,was charged with 1500 mL of dry heptane, 40 μL of water, 4.2 mmol (3.0mL of a 1.4 M solution in heptane) of trimethylaluminum (TMA), and 60 Mlof 1-hexene. The reactor vent was closed and the stirring speed set to900 rpm, and the internal temperature was raised to 95° C., whereafterthe internal pressure was raised from 10 psi (69 kPa) to 16 psi (110kPa) by addition of hydrogen. Ethylene was introduced into the reactorand the internal pressure was increased to 223 psi (1.56 MPa). Finally,0.0507 g of the catalyst prepared as described in Catalyst PreparationExample 16 was added to the autoclave. The reactor pressure wasmaintained at 220-225 psi (1.52-1.55 MPa)for 60 minutes by addition ofethylene, after which time the ethylene flow to the reactor was stoppedand the reactor was cooled to room temperature and vented to theatmosphere. The contents of the autoclave were removed, and all solventswere removed from the product by evaporation, to yield 73.2 g ofpolyethylene resin (ethylene/1-hexene copolymer). This procedure wasrepeated using identical reaction conditions, except that 0.0465 g ofcatalyst described in Catalyst Preparation Example 16 was added to theautoclave, and 85.4 g of polyethylene resin (ethylene/1-hexenecopolymer) product was obtained. The granular resin products of thesetwo slurry polymerization experiments were blended together, and thecombined granular resin was then stabilized with an additive package andmelt homogenized before the Flow Index and the Annular Die Swell weredetermined.

Polymerization Example 17

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,under a slow nitrogen purge at 50° C., and with stirring set to 300 rpm,was charged with 1500 ML of dry heptane, 40 μL of water, 4.2 mmol (3.0mL of a 1.4 M solution in heptane) of trimethylaluminum (TMA), and 60 mLof 1-hexene. The reactor vent was closed and the stirring speed set to900 rpm, and the internal temperature was raised to 95° C., whereafterthe internal pressure was raised from 10 psi (69 kPa) to 16 psi (110kPa) by addition of hydrogen. Ethylene was introduced into the reactorand the internal pressure was increased to 225 psi (1.55 MPa). Finally,0.0579 g of the catalyst prepared as described in Catalyst PreparationExample 17 was added to the autoclave. The reactor pressure wasmaintained at 220-225 psi (1.52-1.55 MPa) for 60 minutes by addition ofethylene, after which time the ethylene flow to the reactor was stoppedand the reactor was cooled to room temperature and vented to theatmosphere. The contents of the autoclave were removed, and all solventswere removed from the product by evaporation, to yield 135.2 g ofpolyethylene resin (ethylene/1-hexene copolymer).

Polymerization Example 18

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,under a slow nitrogen purge at 50° C., and with stirring set to 300 rpm,was charged with 1500 mL of dry heptane, 40 μL of water, 4.2 mmol (3.0mL of a 1.4 M solution in heptane) of trimethylaluminum (TMA), and 60 mLof 1-hexene. The reactor vent was closed and the stirring speed set to900 rpm, and the internal temperature was raised to 95° C., whereafterthe internal pressure was raised from 11 psi (76 kPa) to 17 psi (117kPa) by addition of hydrogen. Ethylene was introduced into the reactorand the internal pressure was increased to 235 psi (1.62 MPa). Finally,0.0560 g of the catalyst prepared as described in Catalyst PreparationExample 18 was added to the autoclave. The reactor pressure wasmaintained at 225-235 psi (1.55-1.62 MPa) for 60 minutes by addition ofethylene, after which time the ethylene flow to the reactor was stoppedand the reactor was cooled to room temperature and vented to theatmosphere. The contents of the autoclave were removed, and all solventswere removed from the product by evaporation, to yield 128.2 g ofpolyethylene resin (ethylene/1-hexene copolymer).

Polymerization Example 19

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,under a slow nitrogen purge at 50° C., and with stirring set to 300 rpm,was charged with 1500 mL of dry heptanc, 40 μL of water, 4.2 mmol (3.0mL of a 1.4 M solution in heptane) of trimethylaluminum (TMA), and 60 mLof 1-hexene. The reactor vent was closed and the stirring speed set to900 rpm, and the internal temperature was raised to 95° C., whereafterthe internal pressure was raised from 10 psi (69 kPa) to 16 psi (110kPa) by addition of hydrogen. Ethylene was then introduced into thereactor and the internal pressure was increased to 224 psi (1.54 MPa).Finally, 0.0589 g of the catalyst prepared as described in CatalystPreparation Example 17 was added to the autoclave. The reactor pressurewas maintained at 219-224 psi (1.51-1.54 MPa) for 60 minutes by additionof ethylene, after which time the ethylene flow to the reactor wasstopped and the reactor was cooled to room temperature and vented to theatmosphere. The contents of the autoclave were removed, and all solventswere removed from the product by evaporation, to yield 135.6 g ofpolyethylene resin (ethylene/1-hexene copolymer).

Table 2 summarizes some of the properties of the resins preparedaccording to the above Comparative Polymerization Examples 1 and 2 andPolymerization Examples 14-19. In addition, properties of somecommercially available resins (Samples A to G) are also shown. TABLE 2Catalyst Ti Resin Prep. Catalyst Polymer Polymer ADS @ ADS @ (Polym.Example Comp. Reactor Catalyst FI (g/10 Density 210 s⁻¹ 6300 s⁻¹ Ex.No.) No. Modifier Type Type min) (g/cm³) (g) (g) Comp. 1 Comp. 11-butanol single bimetallic 17 0.959 0.37 0.51 Comp. 2 Comp. 2 1-butanolsingle bimetallic 19 0.956 0.35 .57 14 14 benzaldehyde single bimetallic15 0.955 0.35 0.68 15 15 benzaldehyde single bimetallic 14 0.954 0.72 1616 benzaldehyde single bimetallic 17 0.952 0.72 17 17 benzaldehydesingle bimetallic 22 0.955 0.38 0.76 18 18 benzaldehyde singlebimetallic 47 0.952 0.37 0.80 19 17 benzaldehyde single bimetallic 320.957 0.84 A⁽¹⁾ N/A N/A single Cr 31 0.954 0.43 0.79 B⁽²⁾ N/A N/A singleCr 41 0.954 0.40-0.46 0.72-0.77 C⁽³⁾ N/A N/A single Cr 22 0.955 0.420.77 D⁽⁴⁾ N/A N/A single Cr 21 0.954 0.44 0.83 E⁽⁵⁾ N/A N/A TandemZiegler 31 0.959 0.33 0.66 F⁽⁶⁾ N/A N/A Tandem Ziegler 30 0.957 0.380.84 G⁽⁷⁾ N/A N/A Tandem Ziegler 25 0.954 0.32 0.57⁽¹⁾Resin HYA 600 available from ExxonMobil Chemical Co.⁽²⁾Resin HYA 301 available from ExxonMobil Chemical Co.⁽³⁾Resin HD5502GA available from BP-AMOCO⁽⁴⁾Resin 5502 available from Fina⁽⁵⁾Resin DH 5973 available from PCD⁽⁶⁾Resin GF 4670 available from Hoechst⁽⁷⁾Resin BC 80 available from Enichem

The results summarized in Table 2 were obtained from the resins producedin a single reactor according to the present invention (PolymerizationExamples 14-19), from commercial blow molding resins produced usingCr-based catalysts in a single reactor (Samples A, B, C. and D), andfrom commercial bimodal MWD blow molding samples produced usingZiegler-type catalysts in tandem reactor processes (Samples E, F, andG). For commercial blow molding applications, optimum Annular Die Swell(ADS) is in the range 0.70-0.79 g at a shear rate of 6300^(s−1) and0.37-0.40 g at a shear rate of 210^(s−1). The commercial unimodal MWDsamples (A-D) in Table 2 show that this range of ADSs is commerciallysignificant. Sample B (HYA 301)is an example of a commercially availableresin produced from a single metal catalyst in a single reactor, whichhas been post-reactor modified to produce a commercially required swell.

Samples E, F and G are examples of commercially available bimodal MWDresins that have been produced in tandem reactor processes. Bimodal MWDresins produced in tandem reactor processes offer advantages overunimodal MWD resins produced commercially in a single reactor, e.g., forblow molding applications. Bimodal resins typically offer much improvedbalance of Environmental Stress Crack Resistance (ESCR) and stiffnesscompared with unimodal resins (i.e., bimodal MWD resins typically havemuch higher ESCR than unimodal resins of the same density). However,bimodal resins produced in tandem reactor processes using Zieglercatalysts often suffer from low resin swell. This is illustrated bySamples E and G.

The resins produced according to Comparative Polymerization Examples 1and 2 show that resins having a bimodal MWD produced in a single reactorwith a bimetallic Ti/Zr catalyst on a support treated with anorganomagnesium component and an alcohol (1-butanol) suffer from lowerthan optimum ADS at the high shear rate of 6300^(s−1).

The resins produced according to Polymerization Examples 14-19illustrate the present invention. Particularly, by changing theformulation of the components of the bimetallic catalyst, one cancontrol the swell properties of the resins produced in a single reactor,and it is possible to produce bimodal MWD resins in a single reactorthat have resin swell properties in the optimum range for commercialblow molding resins. Specifically, when a carbonyl-containing componentsuch as benzaldehyde is used as the modifier in the Ti catalystcomponent formulation in place of an alcohol such as 1-butanol, the ADSof the bimodal resin produced by the corresponding Ti/Zr catalystincreases significantly.

Moreover, Comparative Polymerization Example 2, which employs 1-butanolas Ti catalyst component modifier like Comparative PolymerizationExample 1, but employs the same Zr catalyst component as PolymerizationExamples 14-19, illustrates that changing the Zr catalyst component hasa much smaller effect on the resulting resin swell properties.

Comparative Catalyst Preparation Example 3

Under an inert atmosphere of dry nitrogen. silica (Davison 955, 367 g),previously calcined for 4 hours at 600° C. under dry nitrogen, andisohexane (3600 mL) were added to a 2 gallon (7.6 L) glass vesselcontaining a stirring paddle. The stirring rate was set to 100 rpm, andthe temperature of the silica/isohexane slurry was raised to 51-54° C.for the following reagent addition and drying steps. Next,dibutylmagnesium (0.264 mol, 265.3 g of a 2.42 wt % Mg solution inheptane) was added to the stirred silica slurry. After stirring at 54°C. for 2 hours, 1-butanol (0.251 mol, 18.6 g) was added to the stirredreaction mixture. After stirring for another two hours, titaniumtetrachloride (0.160 mol, 30.3 g) was added to the stirred reactionmixture, and stirring was continued for 2 hours. The liquid phase wasthen removed by evaporation under nitrogen purge, to yield afree-flowing powder.

Comparative Catalyst Preparation Example 4

Under an inert atmosphere of dry nitrogen, silica (Crosfield ES70, 130g), previously calcined for 4 hours at 600° C. under dry nitrogen, andisohexane (780 mL) were added to a 2 liter round-bottom flask fittedwith a paddle stirrer. The flask was placed in a 54° C. oil bath, andthe slurry was stirred vigorously. Next, dibutylmagnesium (0.0936 mol,89.1 mL of a 1.05 M solution in heptane) was added dropwise to thestirred silica slurry at 54° C. over 20 minutes. After stirring at 54°C. for another 50 minutes, benzaldehyde (0.0936 mol, 9.93 g, dilutedwith 40 mL isohexane) was added dropwise to the stirred reaction mixtureover 10 minutes. After stirring at 54° C. for another 50 minutes,titanium tetrachloride (0.0663 mol, 12.6 g, diluted with 40 mLisohexane) was added dropwise to the stirred reaction mixture over 10minutes, and stirring was continued for 50 minutes at 54° C. The liquidphase was then removed by evaporation under nitrogen purge at 54° C., toyield a free-flowing yellow powder.

Comparative Catalyst Preparation Example 5

Under an inert atmosphere of dry nitrogen, silica (Davison 955, 528 g),previously calcined for 4 hours at 600° C. under dry nitrogen, andisohexane (3200 mL) were added to a 2 gallon (7.6 L) glass vessel fittedwith a paddle stirrer. The stirring rate was set to 100 rpm, and thetemperature of the silica/isohexane slurry was raised to 52-56° C. forthe following reagent addition and drying steps. Next, dibutylmagnesium(0.380 mol, 362 mL of a 1.05 M solution in heptane) was added to thestirred silica slurry. After stirring for 1 hour, p-tolualdehyde (0.380mol, 45.7 g, diluted with 200 mL isohexane) was added to the stirredreaction mixture. After stirring for another hour, titaniumtetrachloride (0.269 mol, 51.1 g, diluted with 200 mL isohexane) wasadded to the stirred reaction mixture, and stirring was continued for 1hour. The liquid phase was then removed by evaporation under nitrogenpurge at 54° C., to yield a free-flowing yellow powder.

Catalyst Preparation Example 19

Under an inert atmosphere of dry nitrogen, 2.0 g of thetitanium-containing catalyst component prepared using a proceduresimilar to that described in Comparative Catalyst Preparation Example 3,and isohexane (20 mL) were added to a Schlenk flask containing amagnetic stirring bar. The Schlenk flask was then placed in a 55° C. oilbath for the following reagent addition and drying steps. A solution wasprepared by mixing Cp₂ZrCl₂, (0.73 mmol, 0.213 g) and MAO (80.0 mmol Al,17.5 25 mL of a 4.57 M solution in toluene) in a serum bottle at ambienttemperature, under an inert atmosphere of dry nitrogen. Then 3.5 mL ofthis solution was added dropwise to the stirred titanium catalystcomponent/isohexane slurry at 55° C. over a period of 5 minutes. Afterstirring for an additional 20 minutes at 55° C., the liquid phase wasremoved by evaporation under nitrogen purge to yield a free-flowingbrown powder.

Catalyst Preparation Example 20

The catalyst was prepared in a two-step process:

STEP 1: Under an inert atmosphere of dry nitrogen, silica (CrosfieldES70, 130 g), previously calcined for 4 hours at 600° C. under drynitrogen, and isohexane (780 mL) were added to a 2 liter round-bottomflask fitted with a paddle stirrer. The flask was placed in a 54° C. oilbath, and the slurry was stirred vigorously. Next, dibutylmagnesium(0.0936 mol, 89.1 mL of a 1.05 M solution in heptane) was added dropwiseto the stirred silica slurry at 54° C. over 20 minutes. After stirringat 54° C. for another 50 minutes, benzaldehyde (0.0936 mol, 9.93 g,diluted with 40 mL isohexane) was added dropwise to the stirred reactionmixture over 10 minutes. After stirring at 54° C. for another 50minutes, titanium tetrachloride (0.0663 mol, 12.6 g, diluted with 40 mLisohexane) was added dropwise to the stirred reaction mixture over 10minutes, and stirring was continued for 50 minutes at 54° C. The liquidphase was removed by evaporation under nitrogen purge at 54° C., toyield a free-flowing yellow powder.

STEP 2: Under an inert atmosphere of dry nitrogen, 139 g of thetitanium-containing catalyst component described in Step 1 above, andisohexane (700 mL) were added to a 3 L round-bottom flask fitted with apaddle stirrer. The flask was placed in a 54° C. oil bath, and theslurry was stirred vigorously. A solution was prepared by mixingCp₂ZrCl₂ (8.11 mmol, 2.37 g) and MAO (0.97 mol Al, 196 g of 13.4 wt % Alsolution in toluene) in a Schlenk flask at ambient temperature, under aninert atmosphere of dry nitrogen. This solution was then added dropwiseto the stirred titanium catalyst component/isohexane slurry, which waskept at 54° C., over a period of 130 minutes. The liquid phase wasremoved by evaporation under nitrogen purge at 54° C., to yield afree-flowing brown powder.

Catalyst Preparation Example 21

Under an inert atmosphere of dry nitrogen, 525 g of thetitanium-containing catalyst component described in Comparative CatalystPreparation Example 4 above, and isohexane (3150 mL) were added to a 2gallon (7.6 L) glass vessel containing a stirring paddle. The stirringrate was set to 100 rpm, and the temperature of the vessel was raised to50-56° C. for the following addition and drying steps. A solution wasprepared by mixing Cp₂ZrCI₂ (30.7 mmol, 8.96 g) and MAO (3.68 mol Al,740 g of a 13.4 wt % Al solution in toluene) in a stainless-steel Hokebomb at ambient temperature, under an inert atmosphere of dry nitrogen.This solution was then added to the stirred titanium catalystcomponentlisohexane slurry at ambient temperature, over a period of 60minutes. After stirring at 56° C. for an additional 40 minutes, theliquid phase was removed by evaporation under nitrogen purge to yield afree-flowing brown powder.

Polymerization Experiments for Comparative Catalyst Preparation Examples3-5 and Catalyst Preparation Examples 19-21

The polymerization experiments for Comparative Catalyst PreparationExamples 3-5 and Catalyst Preparation Examples 19-21 were performedusing the same procedure under a standard set of reaction conditions. Atypical example is described below.

A 3.8 liter stainless steel autoclave, equipped with a paddle stirrer,and under a slow nitrogen purge at 50° C. with stirring set to 300 rpm,was charged with 1500 mL of dry heptane, 1.4 mmol (1.0 mL of a 1.4 Msolution in heptane) of trimethylaluminum (TMA), and 60 mL of 1-hexene.The reactor vent was closed and the stirring speed set to 900 rpm, andthe internal temperature was raised to 95° C., whereafter the internalpressure was raised from 10 psi (69 kPa) to 16 psi (110 kPa) by additionof hydrogen. Ethylene was introduced into the reactor and the internalpressure was increased to 225 psi (1.55 MPa). Finally, approximately0.050 g of the catalyst (catalyst precursor) was added to the autoclave.The reactor pressure was maintained at 220-225 psi (1.52-1.55 MPa) for60 minutes by addition of ethylene, after which time the ethylene flowto the reactor was stopped and the reactor was cooled to roomtemperature and vented to the atmosphere. The contents of the autoclavewere removed, and all solvents were removed from the product byevaporation, to yield the polyethylene resin (ethylene/1-hexenecopolymer) product.

The results of these experiments are summarized in Table 3, TABLE 3Amount of PE Mw/Mn Catalyst PE produced by Catalyst (Catalyst ProductTi-only Prep. Metal in Modifier in Precursor) Yield Catalyst ExampleCatalyst Catalyst (g) (g) Component Comp. 3 Ti-only 1-Butanol 0.0504187.8 3.5 Comp. 4 Ti-only Benzaldehyde 0.0511 164.5 5.0 Comp. 5 Ti-onlyp-Tolualdehyde 0.0568 157.4 4.8 19* Ti/Zr 1-Butanol 0.1026 189.4 5.0 20 Ti/Zr Benzaldehyde 0.0545 70.8 6.2 21* Ti/Zr p-Tolualdehyde 0.0982 113.97.1*Polymerizations performed in 2 gallon (7.6 L) autoclave; solvent andreagent amounts were scaled accordingly, to maintain reaction conditionscomparable to those of the 1 gallon (3.8 L) autoclave experiments.

Table 3 shows the polydispersity (Mw/Mn) of the resins produced by theTi-only catalyst components that employ (a) 1-butanol, (b) benzaldehyde,or (c) p-tolualdehyde as modifiers in the preparation. Table 3 alsoshows the effect on the polydispersity of the high molecular weight(HMW) polymer component produced by the same Ti catalyst components inthe finished bimetallic catalysts.

In each case, the polymers were produced under the same polymerizationconditions. The polydispersity of the polymer produced by the Ti-onlycomponents was determined directly from the GPC chromatograms of thepolymer. The polydispersity of the HMW polymer component produced by theTi catalyst components of the bimetallic catalysts was determined by theGPC deconvolution methods described previously.

Table 3 shows that when the 1-butanol “modifier” in the Ti catalystcomponent formulation is replaced with benzaldehyde or p-tolualdehyde,the Mw/Mn of the resin produced by the Ti catalyst component increases.

Table 3 also shows that incorporating the same Ti catalyst componentsinto a Ti/Zr bimetallic catalyst, by treatment with a solution preparedby mixing Cp₂ZrCl₂, and MAO, in each case also increases Mw/Mn of thepolymer produced compared to that of the polymer prepared with theTi-only component. GPC deconvolution of the resins produced by the Ti/Zrbimetallic catalysts indicates that the HMW polymer components typicallyhave Mw/Mn of around 5 for the 1-butanol modified Ti catalystcomponents, compared with Mw/Mn of around 6 to 8 for the polymerproduced from the benzaldehyde and p-tolualdehyde modified Ti catalystcomponents in the finished bimetallic catalysts.

Bimodal polyethylene (PE) resins produced by bimetallic Ti/Zr catalystsystems in which the Ti catalyst component includes benzaldehyde as themodifier show significantly improved resin swell properties comparedwith PE resins produced by bimetallic Ti/Zr catalyst systems in whichthe Ti catalyst component used 1-butanol as the modifier. This higherresin swell may result from the broader polydispersity of the HMWpolymer component produced by the benzaldehyde-modified Ti catalystcomponent, compared with the 1-butanol modified Ti catalyst component.

1. A supported bimetallic catalyst comprising a solid support comprisingat least one non-metallocene transition metal component, at least onemetallocene component, and at least one alumoxane component, wherein thesupport is treated with an organomagnesium component and at least onealdehyde having the general formula:R³—CO—R⁴ wherein R⁴ is a hydrogen, and R³ is selected from the groupconsisting of aliphatic groups containing 1 to 10 carbon atoms, andaromatic groups containing 6 to 12 carbon atoms.
 2. The catalyst ofclaim 1, wherein the support material comprises a solid, particulatematerial.
 3. The catalyst of claim 2, wherein the support materialcomprises silica.
 4. The catalyst of claim 2, wherein theorganomagnesium component comprises at least one dialkylmagnesiumcompound of the general formula (I):R¹ _(m)MgR² _(n)   (I) where R¹ and R² are the same or different alkylgroups containing 2 to 12 carbon atoms and m and n are each 0, 1 or 2,provided that the sum (m+n) is equal to the valence of Mg; themetallocene component comprises at least one compound of the generalformula (III):Cp_(x)MA_(y)   (III) wherein x is at least 1, M is titanium, zirconiumor hafnium, Cp represents optionally substituted cyclopentadienyl,optionally substituted cyclopentadienyl that is part of a bicyclic ortricyclic moiety or, when x is 2, the cyclopentadienyl moieties may belinked by a bridging group, each A is independently selected from ahalogen atom, hydrogen atom, alkyl group and combinations thereof, andthe sum (x+y) is equal to the valence of M; and the aluminoxanecomponent comprises methylaluminoxane (MAO), modified methylaluminoxanes(MMAO) or mixtures thereof.
 5. The catalyst of claim 4, wherein thealkyl groups R¹ and R² each contain 4 to 8 carbon atoms.
 6. The catalystof claim 1, wherein the aldehyde comprises at least one compoundselected from benzaldehyde, p-tolualdehyde, salicylaldehyde,butyraldehyde, 2-pentanone and 3′-methylacetophenone.
 7. The catalyst ofclaim 4, wherein the non-metallocene transition metal componentcomprises at least one compound containing a Group IV or V transitionmetal.
 8. The catalyst of claim 4, wherein Cp is unsubstitutedcyclopentadienyl.
 9. The catalyst of claim 4, wherein Cp representscyclopentadienyl substituted by an alkyl group containing 1 to 8 carbonatoms.
 10. The catalyst of claim 4, wherein the molar ratio oforganomagnesium component to aldehyde ranges from 1:5 to 15:1.
 11. Thecatalyst of claim 10, wherein the atomic ratio of Mg in theorganomagnesium component to transition metal in the non-metallocenetransition metal component ranges from 0.5:1 to 5:1.
 12. The catalyst ofclaim 11, wherein the atomic ratio of transition metal in thenon-metallocene transition metal component to metal in the metallocenecomponent ranges from 1:1 to 30:1.
 13. A process for producinghomopolymer or copolymer of ethylene having bimodal molecular weightdistribution comprising contacting ethylene and optionally one or morecomonomers, with a supported bimetallic catalyst comprising a solidsupport comprising at least one non-metallocene transition metalcomponent, at least one metallocene component, and at least onealumoxane component, wherein the support is treated with anorganomagnesium component and at least one aldehyde having the generalformula:R³—CO—R⁴ wherein R⁴ is a hydrogen, and R³ is selected from the groupconsisting of aliphatic groups containing 1 to 10 carbon atoms, andaromatic groups containing 6 to 12 carbon atoms.
 14. The process ofclaim 13, wherein the support material comprises a solid, particulatematerial.
 15. The process of claim 14, wherein the support materialcomprises silica.
 16. The process of claim 14, wherein theorganomagnesium component comprises at least one dialkylmagnesiumcompound of the general formula (I):R¹ _(m)MgR² _(n)   (I) where R¹ and R² are the same or different alkylgroups containing 2 to 12 carbon atoms and m and n are each 0, 1 or 2,provided that the sum (m+n) is equal to the valence of Mg; themetallocene component comprises at least one compound of the generalformula (III):Cp_(x)MA_(y)   (III) wherein x is at least 1, M is titanium, zirconiumor hafnium, Cp represents optionally substituted cyclopentadienyl,optionally substituted cyclopentadienyl that is part of a bicyclic ortricyclic moiety or, when x is 2, the cyclopentadienyl moieties may belinked by a bridging group, each A is independently selected from ahalogen atom, hydrogen atom, alkyl group and combinations thereof, andthe sum (x+y) is equal to the valence of M; and the aluminoxanecomponent comprises methylaluminoxane (MAO), modified methylaluminoxanes(MMAO) or mixtures thereof.
 17. The process of claim 16, wherein thealkyl groups R¹ and R² each contain 4 to 8 carbon atoms.
 18. The processof claim 13, wherein the aldehyde comprises at least one compoundselected from benzaldehyde, p-tolualdehyde, salicylaldehyde,butyraldehyde, 2-pentanone and 3′-methylacetophenone.
 19. The process ofclaim 16, wherein the non-metallocene transition metal componentcomprises at least one compound containing a Group IV or V transitionmetal.
 20. The process of claim 16, wherein Cp is unsubstitutedcyclopentadienyl.
 21. The process of claim 16, wherein Cp representscyclopentadienyl substituted by an alkyl group containing 1 to 8 carbonatoms.
 22. The process of claim 16, wherein the molar ratio oforganomagnesium component to aldehyde ranges from 1:5 to 15:1.
 23. Theprocess of claim 22, wherein the atomic ratio of Mg in theorganomagnesium component to transition metal in the non-metallocenetransition metal component ranges from 0.5:1 to 5:1.
 24. The process ofclaim 23, wherein the atomic ratio of transition metal in thenon-metallocene transition metal component to metal in the metallocenecomponent ranges from 1:1 to 30:1.
 25. The process of claim 13, whereinthe contacting takes place in a single reactor.
 26. The process of claim25, wherein the reactor is a gas phase reactor.